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(#M40039510) EXAM Numerical Ability question Keep an EYE

4x-5z=16 xz=12 64x^3-125z^3=?

Asked In exam gayathri (9 years ago)

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raj  (9 years ago)

sorry, result will be 15616 not -7424, solve the above expression by putting the given value u'll get it.

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raj  (9 years ago)

(4x)^3-(5z)^3 can be written as (4x-5z)^3+60xz(4x-5z) and solve it using the given information
the result will be -7424

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sneh  (9 years ago)

Ans:- 3520

Solution:-

4x-5z=16
xz=12
64x^3-125z^3=?

(4x)^3-(5z)^3=?

Formula
a^3-b^3 = (a-b)(a^2-ab+b^2)
a^2+b^2 = (a+b)^2-2ab

Then,

(4x)^3-(5z)^3 = (4x-5z)((4x)^2-(4x)(5z)+(5z)^2)
= 16*((4x-5z)^2-3(4x)(5z))
= 16*(256-36)
= 3520

Is this solution Helpfull? Yes (1) | No (3)  

Narasapu Hari prasad  (9 years ago)

ans is 3520
let a-b=4x-5z=12,, ab=xz=12
(a-b)^3=a3-b3-3a^2b+3ab^2
so a^3-b^3==(a-b)^3-3ab(a)+3ab(b)
a^3-b^3=(a-b)^3-3ab(a-b)
substitute values
===>16^3-3*12(16)
====>3520

Is this solution Helpfull? Yes (1) | No   

pancham kumar  (9 years ago)

no,answer will be 15616, by applying formula a^3-b^3=(a-b)^3-3*a*b(a-b)

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