Question

Determine as raízes reais das equações incompletas: A)x²-4x=0 B)-x²+2x=0 C)5x²+10x=0 D)x²-19x=0 E)x²-20=0 F)5x²-15=0 G)x²-4=0 H)4x²+16=0 I)-4x²+28=0 J)(x-7) (x-3)+10x=20 K)3x(x+1)=x(x+2)+4(2-2x)

Answer 1

A) x²-4x= 0
x(x-4)=0
x’= 0 x’’= 4

B) -x²+2x=0
x(2-x)=0
x’=0 x’’= 2

C) 5x²+10x=0
5x(x+2)=0
x’= 0 x”= -2

D) x²-19x=0
x(x-19)=0
x’= 0 x”= 19

E) x²-20=0
x² = 20
x= +/-√20
x’= +2√5 x”= -2√5

F) 5x²-15=0
5x²=15
x²=15/5=3
x’= +√3 x”= -√3

G) x²-4=0
x²= 4
x= +/-√4
x’=2 x”=-2

H) 4x²+16=0
4x²=-16
x²=-16/4
x²=-4
x ∉ R

I) -4x²+28=0
-4(x²-7)=0
x²=7
x’= -√7 x”= √7

J) (x-7)(x-3)+10x=20
(faz a distributiva com o (x-7) e (x-3))
x²-10x+21+10x=20
x²+21-20=0
x²+1=0
x=+/-√1
x’=1 x”=-1