Question

Simplify : $3x(4x-5)+3$ and find values for (i) $x=$ 3 (ii) $x=$$\frac{1}{2}$

Answer 1

$3x(4x-5)+3$
$=3x\times 4x-3x\times 5+3$
$=12x^2-15x+3$

(i) $Forx=3,$
$12x^2+15x+3$
$=12\times (3{)}^2-15\times 3+3$
$=12\times 9-45+3$
$=108-45+3=66$

(ii) For $x=\frac{1}{2}$
$12x^2-15x+3$
$=12\times {\left(\frac{1}{2}\right)}^2-15\times \frac{1}{2}+3$
$=12\times \frac{1}{4}-\frac{15}{2}+3$
$=6-\frac{15}{2}$
$=\frac{12-15}{2}$
$=-\frac{3}{2}$