Answer
$\dfrac{2}{5}z^{2}-\dfrac{3}{10}z+\dfrac{7}{20}$
Work Step by Step
$\Big(\dfrac{1}{4}z^{2}-\dfrac{1}{5}z\Big)-\Big(-\dfrac{3}{20}z^{2}+\dfrac{1}{10}z-\dfrac{7}{20}\Big)$
Remove both parentheses. To remove the second one, change the sign of every term inside it:
$\dfrac{1}{4}z^{2}-\dfrac{1}{5}z+\dfrac{3}{20}z^{2}-\dfrac{1}{10}z+\dfrac{7}{20}=...$
Simplify by combining like terms:
$...=\Big(\dfrac{1}{4}+\dfrac{3}{20}\Big)z^{2}-\Big(\dfrac{1}{5}+\dfrac{1}{10}\Big)z+\dfrac{7}{20}=...$
$...=\dfrac{20+12}{80}z^{2}-\dfrac{10+5}{50}z+\dfrac{7}{20}=...$
$...=\dfrac{32}{80}z^{2}-\dfrac{15}{50}z+\dfrac{7}{20}=\dfrac{2}{5}z^{2}-\dfrac{3}{10}z+\dfrac{7}{20}$
