if 3x - 2y=13 and xy=5 find the value of 27x×x×x - 8y×y×y
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3x-2y=13 (1)
xy=5 (2)
So, y=5/x (3)
Putting (3) in (1)
3x-10/x=13
3x.x-10-13x=0
3x.x-13x-10=0
3x.x-15x+2x-10=0
3x(x-5)+2(x-5)=0
(3x+2)(x-5)=0
So, x=5,-2/3
From (3)
y=1,-15/2.
xy=5 (2)
So, y=5/x (3)
Putting (3) in (1)
3x-10/x=13
3x.x-10-13x=0
3x.x-13x-10=0
3x.x-15x+2x-10=0
3x(x-5)+2(x-5)=0
(3x+2)(x-5)=0
So, x=5,-2/3
From (3)
y=1,-15/2.
bhataastha:
A little bit is left, sorry
27x.x.x-8y.y.y
=27(125)-8(1) =3375-8 =3367. Or=27(-8/27)-8(3375/8) =-8+3375 =3367.
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