(y^2)^-4y^8 simplify

Answer 1

y^2 - 4y^8 = y^2 - (2y^4)^2
= (y + 2y^4)(y - 2y^4)

formulas a^2 - b^2 = (a + b)(a - b)

Answer 2

Or, seeing that the expression as written is meaningless, and assuming the usual carelessness with parentheses,

(y^2)^(-4) * y^8
= y^(2 * -4) * y^8
= y^(-8) * y^8
= y^(-8+8)
= y^0
= 1