2- 1(x+3)-3(x-3) 2-x-3-3x+9 -4x+8 -4(x-2)
x^2 + 8x - 345
x1,2 = -4 +- 1/2√(64 + 4*345) = -4 +- 19 = {-23, 15}
x^2 + 8x - 345 = (x + 23)(x - 15)
8x2-16x-10=0
4x2-8x-5=0
D=(-8)2-4*4*(-5)=64+80=144
x1=(8+12)/(2*4)=20/8=2.5
x2=(8-12)/(2*4)=-4/8=-0.5