I've been recently studiying an Algebra course online, and right now on a review test this expression must be simplified: $$(-2x)^2(-y)^3$$ I distributed the exponent to the terms part and simplified it to $$(4x^2)(-y^3)$$ My question here, it seems to be wrong on the top part simplification as the correct answer that the page graded me was $$(-4x^2)(+y^3)$$ So that means that the result I got before should be multiplied by $-1$ to get this answer, why is this? Isn't my answer exactly the same as this one? Is it part of a standard form to present this? Does the $y$ value must be always positive?
Thanks for the help guys!