Question

If a +b=7 and ab = 12, the value of a^3 + b^3
is :
(1) 91
(2) 595
(3) 343
(4) None of these

Answer 1

So, the ans of this question is (a)91

Answer 2

Answer:

Option (1) is correct.

Step-by-step explanation:

Given:

( a + b ) =7

Cubing both sides ,

We get ,

$(a+b)^{3}$ =$7^{3}$

Formula here used is {$(a + b)^{3}$ = $a^{3}$ + $b^{3}$ +3ab (a + b)}

$a^{3}$ + $b^{3}$ +3ab (a + b)=343

$a^{3}$ + $b^{3}$ + 3× 12 (7 ) =343     {putting the value of ab and a+b we get)

$a^{3}$ + $b^{3}$ + 252=343

$a^{3}$ + $b^{3}$ =343 -252

          =91