а)xy(x+y)-(x2+y2)(x-2y) Упрастите
б)(5с-7p)(7c+5p)-(7c-5p)(5c+7p)
в)(x3+2y)(x2-2y)-(x2+2y)(x3-2y)

xy(x+y) - (x² + y²)(x-2y)=x²y+xy²-(x³+xy²-2x²y-2y³)=x²y+xy²-x³-xy²+2x²y+2y³==2y³- x³ +3x²y(5c-7p)(7c-5p)-(7c-5p)(5c+7p)==35c²-49pc-25pc+35p² - (35c²-25pc+49pc-35p²)==35c² -74pc+35p² - 35c²-24pc+35p²==70p² - 98pc(x³+2y)(x²-2y)-(x²+2y)(x³-2y)==x⁵+2x²y-2x³y-4y²-(x⁵+2x³y-2x²y-4y²)==x⁵+2x²y-2x³y-4y²-x⁵-2x³y+2x²y+4y²==4x²y-4x³y