#### Answer

$(3x-5)(4x-7)$

#### Work Step by Step

Find factors of $ac$ that have a sum of $b$.
Since $ac=420$ and $b=-41$,
find negative factors of $420 $ with a sum of $-41$.
These factors are $-20$ and $-21$.
$12x^{2}-41x+35$
...use the factors to rewrite $bx$.
$=12x^{2}-20x-21x+35$
...factor out the GCF out of each pair of terms.
$=4x(3x-5)-7(3x-5)$
...use the Distributive Property.
$=(3x-5)(4x-7)$