Bài 2:
a: \(xy=\dfrac{\left(x+y\right)^2-x^2-y^2}{2}=2\)
\(x^3+y^3=\left(x+y\right)\left(x^2-xy+y^2\right)=3\cdot\left(5-2\right)=9\)
b: \(xy=\dfrac{5^2-5}{2}=10\)
\(x^3-y^3=\left(x-y\right)^3+3xy\left(x-y\right)\)
\(=125+3\cdot5\cdot10=125+150=275\)