Question

if a+b=4 and ab=5 then a3+b3

Answer 1

Step-by-step explanation:

Refer this pic for solution

Answer 2

Question:

If a + b = 4 and ab = 5 then $a^{3} +b^{3}$ = ?

Given:

a + b = 4

ab = 5

To find: $a^{3} + b^{3}$

Solution:

We can find value by using Identity

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

Putting values

${(4)}^{3} = a^{3} + b^{3} + 3(5)(4) \\ \implies 64 = a^{3} + b^{3} + 60 \\ \implies a^{3} + b^{3} = 64 - 60 \\ \implies a^{3} + b^{3} = 4$

$\huge{Answer}$

$\bold{\boxed{ a^{3} + b^{3} = 4}}$