5(xpatrat-6x+9)-(4xpatrat-12x+9)+x+3=4(xpatrat-4x+4)-3(1-2x+xpatrat)+5 sau 5xpatrat-30x+45-4xpatrat+12x-9+x+3=4xpatrat-16x+16-3+6x-3xpatrat+5 sau xpatrat-17x+39=xpatrat-10x+18(observam ca xpatrat se reduce!) sau -17x+10x=18-39, -7x=-21, deci x=21:7=3