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