Question

Find the value of x3 + y3 when x + y = -5 and xy = 8.​

Answer 1

Answer:

given,

x+y=-5

xy=8

x²+y² = (x+y)²-xy

= (-5)²-8

= 25-8

=17

x³+y³= (x+y)(x²+y²-xy)

=(-5)(17-8)

=(-5)(9)

=-45

Answer 2

The value of x³ + y³ is -5.

Given:

x + y = -5

xy = 8

To Find:

the value of x³ + y³

Solution:

we know that the value of (x + y)³ is given as-

(x + y)³ = x³ + y³ + 3xy(x + y)

substituting the value of x + y and xy into the above equation we get-

(-5)³ = x³ + y³ + 3(8)(-5)

⇒ -125 = x³ + y³ + 24(-5)

x³ + y³ - 120 = -125

x³ + y³ = -125 + 120

x³ + y³ = -5

Thus, the value of x³ + y³ is -5.

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