Question

Cho a+b=5,ab=-2(a<b).hãy tính a^2+b^2;1/a^3+1/b^3;a-b;a^3-b^3

Answer 1

\(a^2+b^2=\left(a+b\right)^2-2ab=5^2-2\cdot\left(-2\right)=29\)

\(a-b=\sqrt{\left(a-b\right)^2+4ab}=\sqrt{5^2+4\cdot\left(-2\right)}=\sqrt{17}\)