Question

x+2y =9 xy=-10 then find x³+8y³


​

Answer 1

Answer:

Since a3+b3=(a+b)3−3ab(a+b)a3+b3=(a+b)3−3ab(a+b), we have

x3+(2y)3=(x+2y)3−6xy(x+2y)=83−(6⋅6⋅8)=8(82–62)=224x3+(2y)3=(x+2y)3−6xy(x+2y)=83−(6⋅6⋅8)=8(82–62)=224. ■ make me branest