Question

1.已知x++y=10,x^3+y^3=100,求x^2+y^2的值

Answer 1

(x+y)^3 = x^3+y^3+3xy(x+y)=10^3=1000

x+y=10,x^3+y^3=100,带入上面可以得到xy=30

x^2+y^2=(x+y)^2-2xy=100-60=40