Question

X*(x+4)=21
Solutiile care sunt?

Answer 1

x(x+4)=21
x²+4x-21=0
x²+7x-3x-21=0
x(x+7)-3(x+7)=0
(x+7)(x-3)=0
x+7=0⇒x=-7
x-3=0⇒x=3
S:x∈{-7,3}