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 = 4} $.
$$ a \cdot c = 32 $$Step 3: Find out two numbers that multiply to $ a \cdot c = 32 $ and add to $ b = 33 $.
Step 4: All pairs of numbers with a product of $ 32 $ are:
PRODUCT = 32 | |
1 32 | -1 -32 |
2 16 | -2 -16 |
4 8 | -4 -8 |
Step 5: Find out which factor pair sums up to $\color{blue}{ b = 33 }$
PRODUCT = 32 and SUM = 33 | |
1 32 | -1 -32 |
2 16 | -2 -16 |
4 8 | -4 -8 |
Step 6: Replace middle term $ 33 x $ with $ 32x+x $:
$$ 8x^{2}+33x+4 = 8x^{2}+32x+x+4 $$Step 7: Apply factoring by grouping. Factor $ 8x $ out of the first two terms and $ 1 $ out of the last two terms.
$$ 8x^{2}+32x+x+4 = 8x\left(x+4\right) + 1\left(x+4\right) = \left(8x+1\right) \left(x+4\right) $$