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CBSE - Class 10 Mathematics Quadratic Equations Worksheet

1.

if x=3 is a solution of the equation , then k = ?

a.

11

b.

-11

c.

13

d.

-13

2.

In a class test, the sum of the marks obtained by a student in English and Hindi is 28. Had he got 3 more marks in English and 4 less marks in Hindi, the product of the marks would have been 180. Find the marks in two subjects.

3.

Solve the following quadratic equation for p:

4.

The sum of squares of two consecutive even number is 340. Find the numbers.

5.

Three consecutive natural number are such that the square of the middle number exceeds the difference of the square of the other teo by 60. Find the numbers.

6.
Represent the following situations in the form of quadratic equations : (iii) Rohan’s mother is $26$ years older than him. The product of their ages (in years) $3$ years from now will be $360$. We would like to find Rohan’s present age.
7.

Solve the following quadratic equation for q:

8.

Find the roots of the following quadratic equation : 2/5a2 - a - 3/5 = 0

9.
Check whether the following are quadratic equations : (i) $(x + 1)^2 = 2(x – 3)$
10.

If x = -2 is a root of the equation , find the value of k so that the roots of the equation are equal.

11.

if x = -4 is a root of the equation , find the value of k so that the roots of the equation are equal.

12.

the perimeter of a rectangle is 82 m and its area is 400 . The breadth of the rectangle is  

a.

25 m

b.

20 m

c.

16 m

d.

9 m

13.
Find the nature of the roots of the following quadratic equations. If the real roots exist, find them: (iii) $2x^2 – 6x + 3 = 0$
14.

Solve for q:

15.

If the roots of the quadratic equation are equal prove that 2b = a + c

16.

The sum of squares of two consecutive odd number is 394. Find the numbers.

17.

If the root of the quadratic equation , a b are equal then prove that b+c = 2a

18.
Check whether the following are quadratic equations : (iv) $(x – 3)(2x +1) = x(x + 5)$
19.

Solve for x:

20.
Check whether the following are quadratic equations : (ii) $x^2 – 2x = (–2)(3 – x)$

Worksheet Answers

1.
Option B

2.

Case 1, English =9, Hindi =19, case 2, English =12, Hindi = 16

3.

x = - (a + b)/2, x = a - b/2

4.

12, 14

5.

9, 10, 11.

Solution:

Given:

1. Rohan’s mother is $26$ years older than Rohan.

2. The product of their ages $3$ years from now will be $360$.

To Find:

Represent the given situation in the form of a quadratic equation in terms of Rohan's present age.

Step 1: Defining the Variables

Let the present age of Rohan be $x$ years.

Since Rohan’s mother is $26$ years older than him, the present age of Rohan’s mother is $(x + 26)$ years.

Step 2: Determining Ages 3 Years from Now

After $3$ years, the age of each person will increase by $3$ years.

Rohan’s age after $3$ years = $(x + 3)$ years.

Rohan’s mother’s age after $3$ years = $(x + 26) + 3 = (x + 29)$ years.

Step 3: Formulating the Equation

According to the problem, the product of their ages $3$ years from now is $360$.

Therefore, we set up the equation:

$(x + 3)(x + 29) = 360$

Step 4: Expanding and Simplifying the Equation

Using the distributive property (FOIL method) to expand the left side:

$x(x + 29) + 3(x + 29) = 360$

$x^2 + 29x + 3x + 87 = 360$

[Combining like terms $29x$ and $3x$]:

$x^2 + 32x + 87 = 360$

Step 5: Bringing the Equation to Standard Form

The standard form of a quadratic equation is $ax^2 + bx + c = 0$. Subtract $360$ from both sides:

$x^2 + 32x + 87 - 360 = 0$

$x^2 + 32x - 273 = 0$

Justification:

The resulting equation $x^2 + 32x - 273 = 0$ is a polynomial of degree $2$, which satisfies the definition of a quadratic equation where $a=1$, $b=32$, and $c=-273$.

Final Answer: The quadratic equation representing the situation is $x^2 + 32x - 273 = 0$, where $x$ is Rohan's present age.

7.

q = a - 2b, q = a + 2b

8.

x = -1/2, 3

Solution:

Given: The equation $(x + 1)^2 = 2(x - 3)$.

To Find: Determine whether the given equation is a quadratic equation.

Definition: A quadratic equation in the variable $x$ is an equation of the form $ax^2 + bx + c = 0$, where $a, b, c$ are real numbers and $a \neq 0$.

Step 1: Expanding the left-hand side (LHS) of the equation.
The expression is $(x + 1)^2$. We use the algebraic identity $(a + b)^2 = a^2 + 2ab + b^2$.
Substituting $a = x$ and $b = 1$:
$(x + 1)^2 = x^2 + 2(x)(1) + (1)^2$
$(x + 1)^2 = x^2 + 2x + 1$

Step 2: Expanding the right-hand side (RHS) of the equation.
The expression is $2(x - 3)$. We use the distributive property $a(b - c) = ab - ac$.
$2(x - 3) = 2(x) - 2(3)$
$2(x - 3) = 2x - 6$

Step 3: Equating the expanded sides and simplifying.
Equating the results from Step 1 and Step 2:
$x^2 + 2x + 1 = 2x - 6$

Step 4: Bringing all terms to one side to form the standard quadratic form.
Subtract $2x$ from both sides:
$x^2 + 2x - 2x + 1 = -6$
$x^2 + 1 = -6$

Add $6$ to both sides:
$x^2 + 1 + 6 = 0$
$x^2 + 7 = 0$

Step 5: Comparing with the standard form $ax^2 + bx + c = 0$.
The equation $x^2 + 7 = 0$ can be written as $1x^2 + 0x + 7 = 0$.
Here, $a = 1$, $b = 0$, and $c = 7$.
Since $a \neq 0$ (as $1 \neq 0$), the equation satisfies the condition for being a quadratic equation.

Final Answer: Yes, the given equation $(x + 1)^2 = 2(x - 3)$ is a quadratic equation because it can be simplified to the form $ax^2 + bx + c = 0$ where $a \neq 0$.

10.

k = 2/3, -1

11.

k = -10/9, 2

12.
Option C

Solution:

Given: A quadratic equation $2x^2 - 6x + 3 = 0$.

To Find: The nature of the roots of the given quadratic equation and, if real roots exist, find their values.

Step 1: Identify the coefficients of the quadratic equation.

A standard quadratic equation is represented as $ax^2 + bx + c = 0$. Comparing the given equation $2x^2 - 6x + 3 = 0$ with the standard form:

  • $a = 2$
  • $b = -6$
  • $c = 3$

Step 2: Determine the nature of the roots using the Discriminant ($D$).

The discriminant of a quadratic equation is given by the formula $D = b^2 - 4ac$.

Substituting the values of $a$, $b$, and $c$:

$D = (-6)^2 - 4(2)(3)$

$D = 36 - 24$

$D = 12$

[Since $D > 0$, the quadratic equation has two distinct real roots.]

Step 3: Apply the Quadratic Formula to find the roots.

The quadratic formula is given by $x = \frac{-b \pm \sqrt{D}}{2a}$.

Substituting the known values into the formula:

$x = \frac{-(-6) \pm \sqrt{12}}{2(2)}$

$x = \frac{6 \pm \sqrt{4 \times 3}}{4}$

$x = \frac{6 \pm 2\sqrt{3}}{4}$

Step 4: Simplify the expression.

Factor out the common term $2$ from the numerator:

$x = \frac{2(3 \pm \sqrt{3})}{4}$

$x = \frac{3 \pm \sqrt{3}}{2}$

Therefore, the two roots are:

$x_1 = \frac{3 + \sqrt{3}}{2}$

$x_2 = \frac{3 - \sqrt{3}}{2}$

Final Answer: The roots are real and distinct. The roots of the equation are $\frac{3 + \sqrt{3}}{2}$ and $\frac{3 - \sqrt{3}}{2}$.


14.

q = ,

15.

2b = a + c, proved

16.

13, 15

17.

b+c = 2a, proved

Solution:

Given: The algebraic equation $(x - 3)(2x + 1) = x(x + 5)$.

To Find: Determine whether the given equation is a quadratic equation.

Definition: A quadratic equation is an equation of the form $ax^2 + bx + c = 0$, where $a, b, c$ are real numbers and $a \neq 0$. The highest power (degree) of the variable in a quadratic equation must be 2.

Step 1: Expanding the Left-Hand Side (LHS)
The LHS is $(x - 3)(2x + 1)$. We apply the distributive property (FOIL method):
$(x - 3)(2x + 1) = x(2x) + x(1) - 3(2x) - 3(1)$
$= 2x^2 + x - 6x - 3$
$= 2x^2 - 5x - 3$ [Combining like terms $x$ and $-6x$]

Step 2: Expanding the Right-Hand Side (RHS)
The RHS is $x(x + 5)$. We apply the distributive property:
$x(x + 5) = x(x) + x(5)$
$= x^2 + 5x$

Step 3: Equating LHS and RHS and Simplifying
Now, set the expanded LHS equal to the expanded RHS:
$2x^2 - 5x - 3 = x^2 + 5x$

To bring the equation into the standard form $ax^2 + bx + c = 0$, we subtract $(x^2 + 5x)$ from both sides:
$(2x^2 - x^2) + (-5x - 5x) - 3 = 0$
$x^2 - 10x - 3 = 0$

Step 4: Verification against the Standard Form
Comparing $x^2 - 10x - 3 = 0$ with the standard form $ax^2 + bx + c = 0$:
Here, $a = 1$, $b = -10$, and $c = -3$.
Since $a \neq 0$ and the highest degree of the variable $x$ is 2, the equation satisfies the definition of a quadratic equation.

Final Answer: Yes, the given equation $(x - 3)(2x + 1) = x(x + 5)$ is a quadratic equation because it simplifies to the form $x^2 - 10x - 3 = 0$.

19.

Solution:

Given: The equation $x^2 - 2x = (-2)(3 - x)$.

To Find: Determine whether the given equation is a quadratic equation.

Definition: A quadratic equation in the variable $x$ is an equation of the form $ax^2 + bx + c = 0$, where $a, b, c$ are real numbers and $a \neq 0$.

Step 1: Simplify the right-hand side (RHS) of the equation.

The given equation is:

$x^2 - 2x = (-2)(3 - x)$

Applying the distributive property of multiplication over subtraction, $a(b - c) = ab - ac$:

$x^2 - 2x = (-2 \times 3) - (-2 \times x)$

$x^2 - 2x = -6 + 2x$

Step 2: Rearrange the equation into the standard form $ax^2 + bx + c = 0$.

To bring all terms to the left-hand side, subtract $2x$ and add $6$ to both sides of the equation:

$x^2 - 2x - 2x + 6 = 0$

Combine the like terms ($-2x$ and $-2x$):

$x^2 - 4x + 6 = 0$

Step 3: Compare with the standard form.

Comparing $x^2 - 4x + 6 = 0$ with the standard quadratic form $ax^2 + bx + c = 0$:

Here, $a = 1$, $b = -4$, and $c = 6$.

[Since $a = 1 \neq 0$, the equation satisfies the condition for being a quadratic equation.]

Conclusion:

Since the highest power of the variable $x$ in the simplified equation is $2$, and the coefficient of $x^2$ is non-zero, the given equation is a quadratic equation.

Final Answer: Yes, the given equation $x^2 - 2x = (-2)(3 - x)$ is a quadratic equation.

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