Question

If a+b=3and a^2+b^2=40 find the value of a^3+b^3

Answer 1

Step-by-step explanation:

Given,

a+b=3

a^2+ b^2= 40

a^3+b^3=?

We know that,

(a+b)2= a^2+b^2+2ab

(3)2= 40+2ab

6=40+2ab

6-40=2ab

-34=2ab

ab=-17

(a+b)3=a^3+b^3+3ab(a+b)

(3)3=a^3+b^3+3(-17)(3)

9=a^3+b^3-153

a^3+b^3=-144

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