3x^2=18xx^2=9x=-3x=32x^2+7x-9=0x=1x=-9/2100x^2-16=0100x^2=16x=0,16x=-0,4x=0,4x^2-16x+63=0(x-9)(x-7)=0x-9=0 или x-7=0x=9 x=7