What is the value of a3+b3 given that a+b=10 and ab=17?
Solution — click to reveal
We realize that a3+b3 is the sum of two cubes and thus can be expressed as (a+b)(a2−ab+b2). From this, we have a3+b3=(a+b)(a2−ab+b2)=(a+b)((a2+2ab+b2)−3ab)=(a+b)((a+b)2−3ab)Now, since a+b=10 and ab=17, we have a3+b3=(a+b)((a+b)2−3ab)=10⋅(102−3⋅17)=10⋅49=490.