Question

найти х3 + y3 если x+y=7 x+y+x2y+xy2=23

Answer 1

x³+y³=(x+y)(x²-xy+y²)=7(x²-xy+y²) x+y=7 (x+y)²=49 x²+2xy+y²=49 x+y+x²y+xy²=23 7+xy(x+y)=23 7xy=16 3xy=16/7 x²-xy+y²=49-16/7=295/7 x³+y³=295