f $x=1,\ y=2$ and $z=5$, find the value of $2x^{2}-3y^{2}+z^{2}$.
Given: $x=1,\ y=2$ and $z=5$.
To do: To find the value of $2x^{2}-3y^{2}+z^{2}$.
Solution:
$2x^{2}-3y^{2}+z^{2}$
$=2(1)^2-3(2)^2+5^2$
$=2-12+25$
$=27-12$
$=15$
Thus, the value of $2x^{2}-3y^{2}+z^{2}=15$.
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