Elementary Technical Mathematics

$-1$
We are given: $x=-1$, $y=2$, $z=-3$ We take into account the order of operations: Parenthesis, Exponents, Multiplication/Division, Addition/Subtraction Thus, we have: $$z^2-5yx^2=(-3)^2-5(2)(-1)^2=9-10=-1 .$$