Question

If x-y=4and xy=21 find the value of x3-y3 by using formula a3-b3 -3ab a-b

Answer 1

Given that : x-y =4
xy= 21
x^3 -y^3 = (x-y)^3 + 3xy (x-y)
= (4)^3 +3 (21) (4)
= 64 + 252
= 316.

Answer 2

Answer:

The value of $x^{3}-y^{3}$ = $316$

Step-by-step explanation:

Given x-y =4 ----(1)

xy = 21 -----(2)

Now ,

The value of $x^{3}-y^{3}$

= $(x-y)^{3}+3xy(x-y)$

= $4^{3} + 3\times 21 \times 4$

/* From (1)& (2) */

= $64 + 252$

= $ 316$

Therefore,

The value of $x^{3}-y^{3}$ = $316$

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