Answer
$-\dfrac{2}{5}x^4+x^3+\dfrac{3}{8}x^2$
Work Step by Step
Consider the given polynomial
$(\dfrac{2}{5}x^4+\dfrac{2}{3}x^3+\dfrac{5}{8}x^2+7)+(-\dfrac{4}{5}x^4+\dfrac{1}{3}x^3-\dfrac{1}{4}x^2-7)$
Need to drop the parentheses.
Thus,
$(\dfrac{2}{5}x^4+\dfrac{2}{3}x^3+\dfrac{5}{8}x^2+7)+(-\dfrac{4}{5}x^4+\dfrac{1}{3}x^3-\dfrac{1}{4}x^2-7)=(\dfrac{2}{5}x^4+\dfrac{2}{3}x^3+\dfrac{5}{8}x^2+7)+(-\dfrac{4}{5}x^4+\dfrac{1}{3}x^3-\dfrac{1}{4}x^2-7)$
$=\dfrac{2}{5}x^4-\dfrac{4}{5}x^4+\dfrac{1}{3}x^3+\dfrac{2}{3}x^3+\dfrac{5}{8}x^2-\dfrac{1}{4}x^2$
$=-\dfrac{2}{5}x^4+x^3+\dfrac{3}{8}x^2$
