Question

x的立方减去3x的平方加5x等于1 y的立方减去3y的平方加5y等于5 求x+y=?

Answer 1

3+y~3-3(x~2+y~2)+5(x+y)=6

1.(x+y)~3=x~3+y~3+3x~2*y+3y~2*x ------ 3+y~3=(x+y)~3-3x~2*y-3y~2*x

2.(x+y)~2=x~2+y~2+2xy ------ 3(x~2+y~2)=3((x+y)~2-2xy)=3(x+y)~2-6xy