Question

What are the solutions of the equation?

Answer 1

Answer:

Option (b) is correct.

The solution of the quadratic equation $x^2+4x=21$  is -7 and 3

Step-by-step explanation:

Consider the given quadratic equation $x^2+4x=21$

This can be rewritten as, $x^2+4x-21=0$

We can solve the quadratic equation using middle term splitting method,

4x can be written as 7x-3x , we get,

$\Rightarrow x^2+4x-21=0$

$\Rightarrow x^2+7x-3x-21=0$

Taking terms common, we get,

$\Rightarrow x(x+7)-3(x+7)=0$

Thus, $\Rightarrow (x-3)(x+7)=0$

Thus, we get (x-3)= 0 or (x+7)= 0  

this gives x = 3 or x = -7

Thus, the solution of the quadratic equation $x^2+4x=21$  is -7 and 3