Question

if x+y=-8 and xy=-48 then evaluate x^3 + y^3​

Answer 1

Answer:

128

Step-by-step explanation:

(x^3+y^3) = (x + y)(x^2+y^2+xy)

               = 8 * [ (x+y)^2 - 2xy + xy]

               = 8 * [ 8^2 - 48]

               = 128

Answer 2

x=-8-y _________eq 1

xy=-48 ________eq 2

putting value of x in equation 2

(-8-y)y=-48

-y^2-8y=-48

-(y^2+8y)=-48

y^2+8y-48=0

y^2+12y-4y-48=0

y(y+12)-4(y+12)=0

(y+12)(y-4)=0

therefore y=-12,4

then x=4,-12

x^3+y^3

=-1728+64

=-1664