If (a-b)=4 and a b=2, then (a^{3}-b^{3} ) is equal to:

SSC CGL 13 Jun 2019 Shift 1 Paper

Question : 52 of 100

Marks: +1, -0

(a-b)=4

and

a b=2,

then

\ (a^{3}-b^{3}\ )

is equal to:

Solution:

a^{3}-b^{3}=4

a^{3}-b^{3}=(a-b)\ (a^{2}+b^{2}+a b\ )

=(4)\ [(a-b)^{2}+3 a b\ ]

=(4)[16+6]=(4)[22]=88

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