Doua metode, stiind ca inmultirea este comutativa :
I : Le inmultim in ordinea data :
(5x²-13x+6)(5x²+42x-27)=25x⁴+210x³-135x²-65x³-546x²+351x+30x²+252x-162
=25x⁴+145x³-651x²+603x-162
II : Inmultim prima si a treia paranteza, folosind formula de calcul prescurtat (a-b)²=a²-2ab+b²
(25x²-30x+9)(x²+7x-18)=25x⁴+175x³-450x²-30x³-210x²+540x+9x²+63x-162
=25x⁴+145x³-651x²+603x-162
