Step-by-step explanation:
polynomial identities means equations where the left and the right side are always identical (no matter what values we use for the variables).
so,
A is not.
(x + 2)³ = x³ + 8
(x+2)(x+2)(x+2) = x³ + 8
(x² + 4x + 4)(x+2) = x³ + 8
x³ + 4x² + 4x + 2x² + 8x + 8 = x³ + 8
x³ + 6x² + 10x + 8 is definitely not generally the same as x³ + 8
B is not.
x⁶ + x = (x-1)(x⁵ + x⁴ + x³ + x² + x)
x⁶ + x = x⁶ + x⁵ + x⁴ + x³ + x² - x⁵ - x⁴ - x³ - x² - x
x⁶ + x = x⁶ - x
that is definitely not generally equal.
C is an identity
(x² - 1)(x⁴ + x² + 1) = x⁶ - 1
x⁶ + x⁴ + x² - x⁴ - x² - 1 = x⁶ - 1
x⁶ - 1 = x⁶ - 1
yes, identical.
D is not.
(x+1)⁴ = x⁴ + x³ + x² + x + 1
(x+1)²(x+1)² = x⁴ + x³ + x² + x + 1
(x²+2x+1)² = x⁴ + x³ + x² + x + 1
x⁴ + 2x³ + x² + 2x³ + 4x² + 2x + x² + 2x + 1 =
x⁴ + 4x³ + 6x² + 4x + 1
that is definitely not generally the same as
x⁴ + x³ + x² + x + 1
E is an identity
(x+1)(x⁴ - x³ + x² - x + 1) = x⁵ + 1
x⁵ - x⁴ + x³ - x² + x + x⁴ - x³ + x² - x + 1 =
x⁵ + 1 = x⁵ + 1
yes, identical.
F is an identity
(x³-1)(x³+1) = x⁶ - 1
x⁶ + x³ - x³ - 1 = x⁶ - 1
x⁶ - 1 = x⁶ - 1
yes, identical.
