Question

a)-5(-2x+3)-3xao quadrado=1-2x ao quadrado
b)2x(x-4)+5=-xao quadrado+7x-7
c)(x+2)(2x-3)=5x ao quadrado+x-114

Answer 1

Resposta A:
-5(-2x+3)-3x²=1-2x²
10x-15-3x²=1-2x²
-3x²+2x²+10x-15-1=0
-x²+10x-16=0 (×-1)
x²-10x+16=0
Δ=(-10)²-4×1×16
Δ=100-64
Δ=36
6
x'=-10+6/2=-4/2=-2
x"=-10-6/2=-16/2=-8

Resposta B:
2x(x-4)+5=-x²+7x-7
2x²-8x+5=-x²+7x-7
2x²+x²-8x-7x+5+7=0
3x²-15x+12=0
Δ=(-15)²-4×3×12
Δ=225-144
Δ=81
9
x'=15+9/2×3=24/6=4
x"=15-9/2×3=6/6=1

Resposta C:
(x+2)(2x-3)=5x²+x-114
2x²+x-6=5x²+x-114
2x²-5x²+x-x-6+114=0
-3x²+108=0 (×-1)
3x²-108=0
x(3x-108)=0
x'=0
       3x-108=0
       3x=108
       x=108/3
       x"=36