Question

if one root of the equation x^2+ bx + 8=0 is 4 and the roots of the equation x^2+ bx+ c=0 are equal find the value of c

Answer 1

Hey friend, Harish here.

Here is your answer.

Given :

i) Roots of both the equations are equal.

ii) One root is 4.

iii) Two equations.

To Find:

The value of c .

Solution:

Let the unknown root be x

In 1st equation, 

Product of roots = 8

4 × x = 8.

x = 2.

Therefore the roots are 4 and 2.

In (ii) equation.

Product of roots = c.

4 × 2 = c

c = 8.
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2nd Approach. 

As both the equation has equal roots, and coefficient of x² is same,

We can compare both the equations.

By comparing we get c = 8.
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Hope my answer is helpful to you.

Answer 2

Answer:

Given:

i) Roots of both the equations are equal.

ii) One root is 4.

iii) Two equations.

To Find:

The value of c.

Solution:

Let the unknown root be x

In 1st equation,

Product of roots = 8

4 × x = 8.

x= 2.

Therefore the roots are 4 and 2.

In (ii) equation.

Product of roots = c.

4 x 2 = c

C = 8.

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2nd Approach.

As both the equation has equal roots, and coefficient of x is same,

We can compare both the equations. By comparing we get c = 8.