Odpowiedź:
c) 2x(x+1)+6=4(2-3x)-4
2x²+2x+6= 8-12x-4
2x²+2x+6-8+12x+4=0
2x²+14x+2=0/:2
x²+7x+1=0
a= 1 b=7 c= 1
Δ= b²-4ac
Δ= 7²-4*1*1
Δ=49-4
Δ=45
√Δ=√45= √9*5 = 3√5
x₁= -b-√Δ/2a
x₁= -7-3√5/2*1
x₁= -7-3√5/2
x₂= -b+√Δ/2a
x₂= -7+3√5 /2*1
x₂= -7+3√5/2
