Question

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

Answer 1

$3x(4x-5)+3$

$=12x^2-15x+3$

$=3(4x^2-5x+1)$

$=3(4x^2-4x-x+1)$

$=3(4x(x-1)-1(x-1))$

$=3(x-1)(4x-1)$ at $x=\frac{1}{2}$

$=3(\frac{1}{2}-1)(4\times \frac{1}{2}-1)$

$=3\times \frac{-1}{2}\times (2-1)$

$=\frac{-3}{2}$