Question

if x+y =2 find x cube +y cube +6xy-8

Answer 1

Answer:

Step-by-step explanation:

x+y=2

x^3+y^3+6xy-8=??

(x+y)^3=x^3+y^3+3xy×(x+y)

Substituting the value x+y:

(2)^3=x^3+y^3+3xy×(2)

8=x^3+y^3+6xy

Substituting the valu of x^3+y^3+6xy in x^3+y^3+6xy-8:

x^3+y^3+6xy-8

= 8-8

=0

Answer 2

x+y=2 ---(1)

cubing both sides

(x+y)3=(2)3

x3+y3+3xy(x+y)=8

using equation (1)

x3+y3+3xy(2)=8

x3+y3+6xy= 8

x3+y3+6xy-8= 0