Step 1: Identify constants $ a $ , $ b $ and $ c $.
$ a $ is a number in front of the $ x^2 $ term $ b $ is a number in front of the $ x $ term and $ c $ is a constant. In this case:
Step 2: Multiply the leading coefficient $\color{blue}{ a = 4 }$ by the constant term $\color{blue}{c = 24} $.
$$ a \cdot c = 96 $$Step 3: Find out two numbers that multiply to $ a \cdot c = 96 $ and add to $ b = -35 $.
Step 4: All pairs of numbers with a product of $ 96 $ are:
PRODUCT = 96 | |
1 96 | -1 -96 |
2 48 | -2 -48 |
3 32 | -3 -32 |
4 24 | -4 -24 |
6 16 | -6 -16 |
8 12 | -8 -12 |
Step 5: Find out which factor pair sums up to $\color{blue}{ b = -35 }$
PRODUCT = 96 and SUM = -35 | |
1 96 | -1 -96 |
2 48 | -2 -48 |
3 32 | -3 -32 |
4 24 | -4 -24 |
6 16 | -6 -16 |
8 12 | -8 -12 |
Step 6: Replace middle term $ -35 x $ with $ -3x-32x $:
$$ 4x^{2}-35x+24 = 4x^{2}-3x-32x+24 $$Step 7: Apply factoring by grouping. Factor $ x $ out of the first two terms and $ -8 $ out of the last two terms.
$$ 4x^{2}-3x-32x+24 = x\left(4x-3\right) -8\left(4x-3\right) = \left(x-8\right) \left(4x-3\right) $$