x^2-4x-21=0 solving quadratic Equations

Question

solving quadratic Equations

 

Answer 1

X^2-4X-21 = 0

Factorize the above equation.

x^2-7x+3x-21 = 0

x(x-7)+3(x-7) = 0

(x-3)(x-7) = 0

x-3 = 0                       or                   x-7 = 0

Add 3 to each side.                   Add 7 to each side.

x-3+3 = 0+3                            x-7+7 = 0+7

x = 3                                        x = 7

Solution of quadratic equation x = 3,7

Comments

check your answer
x(x-7)+3(x-7) = 0
(x + 3)(x - 7) = 0
x = -3 or x = 7

Answer 2

Therefore the solution of the given quadratic equation is x = 7 and x = -3.