Question

a+b= -1, then the value of
Value of a cube +b cube -3ab​

Answer 1

Aim:-

We know from the given question that, $a+b=-1$. With the given information, we are finding the value of $a^3+b^3-3ab$.

Solution:-

According to the question,

$a+b=-1$

So, by cubing on both the sides LHS and RHS, we get,

$(a+b)^3=(-1)^3$

As we know, $(a+b)^3=a^3+b^3+3ab(a+b)$

So, $a^3+b^3+3ab(a+b)=(-1)^3$

Since, $(-1)^3=-1$

So, $a^3+b^3+3ab(a+b)=-1$

By substituting the value of $(a+b)$ which is given in the question,

$a^3+b^3+3ab(-1)=-1$

∴ $\boxed{a^3+b^3-3ab=-1}$

Answer 2

Refer the attachment...