Question

câu 1 

cho a+b=-5;ab=3.Tính giá trị biểu thức \(^{a^3}\)+\(b^3\) 

 

Answer 1

\(a^3+b^3=\left(a+b\right)\left(a^2-ab+b^2\right)\)

            \(=\left(a+b\right)\left(a^2+b^2-ab\right)\) 

            \(=\left(a+b\right)\left[\left(a+b\right)^2-ab\right]\)\(\left(1\right)\)

Thay \(a+b=-5;ab=3\) vào \(\left(1\right):\)

\(\left(-5\right).\left[\left(-5\right)^2-3\right]=-110\)

 

Answer 2

tham khảo

https://hamchoi.vn/cau-hoi/10743/gia-tri-cua-bieu-thuc-q-a3-b3-biet-a-b-5-va-ab-3