Question

1. $(-2x^{5}y^{7})^{3}+7x^{15}y^{21}$

Explanation:

Step1: Expand the cubed term

Apply exponent rules: $(ab)^n=a^n b^n$ and $(a^m)^n=a^{mn}$
$$(-2x^5y^7)^3 = (-2)^3 \cdot (x^5)^3 \cdot (y^7)^3 = -8x^{15}y^{21}$$

Step2: Combine like terms

Add the expanded term to the second term
$$-8x^{15}y^{21} + 7x^{15}y^{21}$$

Answer:

$-x^{15}y^{21}$