Question

$\text{If}a=2,b=3,c=4,\text{find the value of:}$

$\text{(a)}3a-b+2c$
$\text{(b)}{a}^2-b^2+c^2$
$\text{(c)}ab-3abc-2ac$
$\text{(d)}{a}^{2}b+bc-3c^3-2abc$

Answer 1

$\text{(a)}3a-b+2c=3\times 2-3+2\times 4=6-3+8=11$
$\text{(b)}{a}^2-b^2+c^2=2^2-3^2+4^2=4-9+16=11$
$\text{(c)}ab-3abc-2ac=2\times 3-3\times 2\times 3\times 4-2\times 2\times 4=6-72-16=-82$
$\text{(d)}{a}^{2}b+bc-3c^3-2abc=2\times 2\times 3+3\times 4-3\times 4\times 4\times 4-2\times 2\times 3\times 4=12+12-192–48=-216$