a)2x5-644=0 b)x3-x2+9x-9=0 c)x3-6x2+9x=0 d)x3+3x2-4x=0

a) 2x5-644=0 2x*5=-644 /:5 2x=-128.8 / :2 x=64.4 b) x3-x2+9x-9=0 x3-x2+9x=-9 10x=-9 /:10 x=-0.9 c) x3-6x2+9x=0 6x-6x2=0 6x-12x=0 -6x=0 / -6 x=0 d) x3+3x2-4x=0 -x=0