Question

If $p=-2,q=1$ and $r=3$ find the value of
( a ) $p^2+q^2-r^2$
( b ) $p-q-r$
( c ) $p^3+q^3+r^3+3pqr$

Answer 1

Given $p=-2$, $q=1$, $r=3$

(a) $p^2+q^2-r^2=(-2{)}^2+(1{)}^2-(3{)}^2$

$=4+1-9$

$=5-9$

$=-4$

(b) $p-q-r=(-2)-\left(1\right)-\left(3\right)$

$=-2-1-3$

$=-6$

(c) $p^3+q^3+r^3+3pqr=(-2{)}^3+(1{)}^3+(3{)}^3+3(-2\left)\right(1\left)\right(3)$

$=-8+1+27-18$

$=-26+28$

$=2$.