Question 31

If $$x + y = 4$$, then what is the value of $$x^{3} +y^{3} +12xy$$?

Solution

Given : $$x+y=4$$ -----------(i)

Cubing both sides, we get :

=> $$(x+y)^3=(4)^3$$

=> $$x^3+y^3+3xy(x+y)=64$$

=> $$x^3+y^3+3xy(4)=64$$

=> $$x^3+y^3+12xy=64$$

=> Ans - (C)


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