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 $\color{blue}{ a = 24 }$ by the constant term $\color{blue}{c = -4} $.
$$ a \cdot c = -96 $$Step 3: Find out two numbers that multiply to $ a \cdot c = -96 $ and add to $ b = -29 $.
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 $\color{blue}{ b = -29 }$
PRODUCT = -96 and SUM = -29 | |
-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 $ -29 x $ with $ 3x-32x $:
$$ 24x^{2}-29x-4 = 24x^{2}+3x-32x-4 $$Step 7: Apply factoring by grouping. Factor $ 3x $ out of the first two terms and $ -4 $ out of the last two terms.
$$ 24x^{2}+3x-32x-4 = 3x\left(8x+1\right) -4\left(8x+1\right) = \left(3x-4\right) \left(8x+1\right) $$