Question

If $a=2$ and $b=3$, find the value of
(i) $2a-3b$ (ii) $5a^2-2ab$ (iii) $a^3-b^3$

Answer 1

Given $a=2$ and $b=3$

$\left(i\right)2a-3b=2\left(2\right)-3\left(3\right)=4-9=-5$

$\left(ii\right)5a^2-2ab=5(2{)}^2-2(2\left)\right(3)=20-12=8$

$\left(iii\right)a^3-b^3=(2{)}^3-(3{)}^3=8-27=-19$