Question

If a + b =6 and ab = 8 find$a^3+b^3$

• A. 12
• B. 46
• C. 72
• D. 84

Answer 1

Answer:

C. 72

$(a+b)^3=a^3+b^3+3a^b+3ab^2$

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

$=6^3-3\times8(6)$

$=216-144$

$=72$