Question

If x-y=5 find the value of x3 - y3-15xy

Answer 1

Answer:

125

Step-by-step explanation:

x - y = 5

cubing on both sides

(x-y)³ = 5³

⇒x³ - y ³ - 3xy ( x-y) = 125

⇒ x³ -  y³ - 3xy (5) = 125

⇒ x³ - y³ - 15xy = 125

Answer 2

Given:

The given expression is

${x}^{3} - {y}^{3} - 15xy$

The value of x-y=5.

To find:

The value of the expression.

Solution:

To determine the value of the expression we have to follow the below steps as follows-

The given expression is

${x}^{3} - {y}^{3} - 15xy$

It can be simplified as follows-

$(x - y)( {x}^{2} + xy + {y}^{2} ) - 15xy \\ {(x - y) ((x - y)}^{2} + 2xy + xy) - 15xy$

Now putting the value of x-y we get-

$5( {5}^{2} + 3xy) - 15xy \\ 5 \times 25 + 15xy - 15xy \\ 125$

The value of the above expression is 125.