Question

If a3 + b3 = 72 and ab = 8 , then what is the value of a + b?

Answer 1

Answer:

a+b = 6

Step-by-step explanation:

Formula used:

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

Given:

$a^3+b^3=72$ and $ab=8$

Now,

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

$(a+b)^3=72+3(8)(a+b)$

$(a+b)^3=72+24(a+b)$

$x^3=72+24x\:\:where\:x=a+b$

$x^3-24x-72=0$

clearly x=6 will satiasfy this equation.

$\implies\:a+b=6$

Answer 2

Step-by-step explanation:

hope this will help you

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