Răspuns :
x²-2x=8
x²-2x-8=0
x²-4x+2x-8=0
x(x-4)+2(x-4)=0
(x-4)(x+2)=0
x-4=0⇒x=4
x+2=0⇒x=-2
S:x∈{4,-2}
x²-2x-8=0
x²-4x+2x-8=0
x(x-4)+2(x-4)=0
(x-4)(x+2)=0
x-4=0⇒x=4
x+2=0⇒x=-2
S:x∈{4,-2}
x²-2x=8
x²-2x-8=0
a=1
b=-2
c=-8
∆=b²-4ac
∆=(-2)²-4×1×(-8)
∆=4-4×(-8)
∆=4+32
∆=36
x(1,2)=(-(-2)±√∆)/2a
x(1,2)=(2±√36)/2×1
x(1)=(2+6)/2 => x(1)=8/2 => x(1)=4
x(2)=(2-6)/2 => x(2)=-4/2 => x(2)=-2
x²-2x-8=0
a=1
b=-2
c=-8
∆=b²-4ac
∆=(-2)²-4×1×(-8)
∆=4-4×(-8)
∆=4+32
∆=36
x(1,2)=(-(-2)±√∆)/2a
x(1,2)=(2±√36)/2×1
x(1)=(2+6)/2 => x(1)=8/2 => x(1)=4
x(2)=(2-6)/2 => x(2)=-4/2 => x(2)=-2
