Given : $$a^3 - b^3 = 26$$
Also, $$a-b=2$$
Cubing both sides,
=> $$(a-b)^3=(2)^3$$
=> $$a^3-b^3-3ab(a-b)=8$$
=> $$26-3ab(2)=8$$
=> $$6ab=26-8=18$$
=> $$ab=\frac{18}{6}=3$$ -------------(i)
Also, $$a^3-b^3=(a-b)(a^2+b^2+ab)$$
=> $$26=2(a^2+b^2+3)$$
=> $$a^2+b^2+3=\frac{26}{2}=13$$
=> $$a^2+b^2=13-3=10$$ --------------(ii)
$$\therefore$$Â $$(a + b)^2$$ = $$a^2+b^2+2ab$$
Using equations (i) and (ii), we get :
= $$10+2(3)=16$$
=> Ans - (C)
Create a FREE account and get: