Simplify -1/5z^2+3/5z^2

$- \frac{1}{5} z^{2} + \frac{3}{5} z^{2}$

Simplify each term.

Combine $z^{2}$ and $\frac{1}{5}$ .

$- \frac{z^{2}}{5} + \frac{3}{5} z^{2}$

Combine $\frac{3}{5}$ and $z^{2}$ .

$- \frac{z^{2}}{5} + \frac{3 z^{2}}{5}$

Simplify terms.

Combine the numerators over the common denominator.

$\frac{- z^{2} + 3 z^{2}}{5}$

Add $- z^{2}$ and $3 z^{2}$ .

$\frac{2 z^{2}}{5}$