Question

What are the roots of the equation x² + 4x - 16 = 02

(1) 2 ± 2√5
(3) 2 ± 4√5
(2) -2 ± 2√5
(4) -2 ± 4√5

Answer 1

Hello !

x² + 4x - 16 = 0

it's a quadratic equation : ax² + bx + c

x = (-b ± √(b² - 4ac)/2a

= (-4 ± (4² - 4*1*(-16))/(2*1)

= (-4 ± √80)/2

= (-4 ± 4√5)/2

= -2 ± 2√5