# NCERT Class 10 Chapter 5 Quadratic Equations Official CBSE Board Sample Problems Short Answer

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## Question

If- 5 is a root of the quadratic equation and the quadratic equation has equal roots, find the value of k

### Solution

is the root of the quadratic equation

Now, given that equation has equal roots

I.e. has equal roots

I.e. has equal roots

(For equal roots, D = 0, i.e.]

## Question

If and are roots of the quadratic equations, find the values ofaand b.

### Solution

(x = is the root of equation (i))

...(ii)

[ is the root of equation (i)]

..(iii)

Putting the value of b from (iii) in (ii), we get

Putting a = 3 in (iii), we have

## Question

A two digit number is four times the sum of the digits. It is also equal to 3 times the product of digits. Find the number.

### Solution

Let ones digit of number = x

Let tens digit of number = y

Number will be

According to question,

…(i)

and ...(ii)

Putting from (i) in (ii), we get,

and )

The required number .

Solve for x:

## Question

If the roots of the quadratic equation are equal, prove that.

### Solution

For equal roots, discriminant, D = 0

## Question

The following picture shows the shape of a certain grass patch. If the area of the patch is , find k.

### Solution

The total area

Since the area is

Since the length cannot be negative, .

and

## Question

Find 2 numbers that sum to 21 and the sum of the squares is 261.

### Solution

The numbers are 15 and 6.

Hence,and

## Question

Find the roots of the following equations:

### Solution

On simplifying we get

## Question

If p and q are the roots of the equation , then find the value of p and q.

### Solution

Since p and q are the roots of this equation, Hence:. Hence,

Hence,

## Question

Find the value of k for which the quadratic equation has two real and equal roots.

For equal roots

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