Question

Question 4(a)
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) $Forx=3,$
$12x^2+15x+3=12(3{)}^2-15\times 3+3$
$=12\times 9-45+3=108-45+3=66$
(ii) For $x=\frac{1}{2}$
$12x^2-15x+3=12\times {\left(\frac{1}{2}\right)}^2-15\times \frac{1}{2}+3=12\times \frac{1}{4}-\frac{15}{2}+3$
$=6-\frac{15}{2}=\frac{12-15}{2}=\frac{-3}{2}$