Question

X²+x = -1 then x³-1 =?​

Answer 1

Answer:

0

Step-by-step explanation:

x²+x=-1, middle term spread

then,

x²+x+1=0

x²+x+x+1=0

x(x+1)-1(x+1)=0

then, two values of x

(x-1) (x+1)

x=1 ,x=-1

x³-1=(1)³-1= 1-1= 0

Answer 2

Step-by-step explanation:

cube both sides

(x² + x)³=(-1)³

[(a+b)³ = a³+ b³+ 3ab(a+b)]

x⁶ + x³ + 3x² × x(x² + x) = -1

x⁶ + x³ - 3x³ = -1

x³(x³+1-3) = -1

x³(x³-2) = -1

x³-1 = 0