Question

2. If x + y = 3 and xy = -18, then find the value
of x³ + y³​

Answer 1

Answer:

Step-by-step explanation:

given,

x+y=3....(1)

xy=-18.....(2)

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

we dont have value of x^2+y^2 with us

so lets find x^2+y^2 from (1)

squaring on both sides

(x+y)^2=3^2=9

x^2+y^2+2xy=9

x^2+y^2-2*18=9

x^2+y^2=9+36=45

so

x^3+y^3=(3)(45+18)

=3*63=189

Answer 2

Answer:

x^3 + y^3 =(a+ b)^ 3-3ab(a+b)

Step-by-step explanation:

now put the values as well

x^3+ y^3= (3)^3 - 3*-18(3)

=27+9*18

x^3+y^3 = 162+27 = 189