Question

a+b= 4 and ab =3 find the value of à³+b³

Answer 1

a³+b³ = (a+b)(a²+b²-ab) ---(1)

a²+b² = (a+b)²-2ab ---(2)

Substituting the value of a²+b² from equation 2 in equation 1, we have :

a³+b³ = (a+b)[{(a+b)²-2ab}-ab] --(3)

We are given with :

a+b = 4 and ab = 3

Then using this data in equation 3) we have :

a³+b³ = 4[{4² -2(3)}-3]

= 4[16-6-3]

= 4 × 7

= 28

The required value of a³+b³ = 28.

Answer 2

Answer:

a3 + b3 = 28

Step-by-step explanation:

a+b = 4

then,

(a+b)whole cube = 64

=> a3 + b3 + 3ab(a+b) = 64

=> a3 + b3 + 3 x 3 x 4 = 64

=> a3 + b3 + 36 = 64

=> a3 + b3 = 64 - 36

=> a3 + b3 = 28