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 $\color{blue}{ a = 8 }$ by the constant term $\color{blue}{c = 24} $.
$$ a \cdot c = 192 $$Step 3: Find out two numbers that multiply to $ a \cdot c = 192 $ and add to $ b = -67 $.
Step 4: All pairs of numbers with a product of $ 192 $ are:
PRODUCT = 192 | |
1 192 | -1 -192 |
2 96 | -2 -96 |
3 64 | -3 -64 |
4 48 | -4 -48 |
6 32 | -6 -32 |
8 24 | -8 -24 |
12 16 | -12 -16 |
Step 5: Find out which factor pair sums up to $\color{blue}{ b = -67 }$
PRODUCT = 192 and SUM = -67 | |
1 192 | -1 -192 |
2 96 | -2 -96 |
3 64 | -3 -64 |
4 48 | -4 -48 |
6 32 | -6 -32 |
8 24 | -8 -24 |
12 16 | -12 -16 |
Step 6: Replace middle term $ -67 x $ with $ -3x-64x $:
$$ 8x^{2}-67x+24 = 8x^{2}-3x-64x+24 $$Step 7: Apply factoring by grouping. Factor $ x $ out of the first two terms and $ -8 $ out of the last two terms.
$$ 8x^{2}-3x-64x+24 = x\left(8x-3\right) -8\left(8x-3\right) = \left(x-8\right) \left(8x-3\right) $$