Question

$x^{2} +4x-21$

Answer 1

x²+4x-21=0

a = 1

b = 4

c = -21

∆ = 4² - 4 • 1 • (-21)

∆ = 16 + 84

∆ = 100

x = - (+4) ± √∆/2 • 1

x = -4 ± 10/2

x¹ = -4 + 10/2 = 6/2 = 3

x² = -4 -10/2 = -14/2 = -7