SSC CHSL 15 Oct 2020 Shift 1 Paper

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Question : 56 of 100

Marks: +1, -0

If

a

and

b

are two positive real numbers such that,

a+b=20

and

a b=4

, then the value of

a^{3}+b^{3}

is

7760
240
8000
8240

Solution:

Given,

a+b=20

and

a b=4

We know that,

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

(20)^{3}=a^{3}+b^{3}+3 ×4 ×20

⇒

a^{3}+b^{3}=8000-240=7760

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