Question

Encontre os valores reais de x tais que : a)x²-7x=0
b)2x²-16x=0
c)5x²+20x=0
d)-2x²-42x=0

Answer 1

a)x²-7x=0
x.x-7x=0
x.(x-7)=0
x=0 ou x-7=0
x=0+7
x=7

b)2x²-16x=0
2x.x-16x=0
x.(2x-16)=0
x=0 ou 2x-16=0
2x=0+16
2x=16
x=16÷2
x=8

c)5x²+20x=0
5x.x+20x=0
x.(5x+20)=0
x=0 ou 5x+20=0
5x=0-20
5x=-20
x=-20÷5
x=-4

d)-2x²-42x=0
-2x.x-42x=0
x.(-2x-42)=0
x=0 ou -2x-42=0
-2x=0+42
-2x=42
x=42÷-2
x-21