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 $\color{blue}{ a = 3 }$ by the constant term $\color{blue}{c = 50} $.
$$ a \cdot c = 150 $$Step 3: Find out two numbers that multiply to $ a \cdot c = 150 $ and add to $ b = -25 $.
Step 4: All pairs of numbers with a product of $ 150 $ are:
PRODUCT = 150 | |
1 150 | -1 -150 |
2 75 | -2 -75 |
3 50 | -3 -50 |
5 30 | -5 -30 |
6 25 | -6 -25 |
10 15 | -10 -15 |
Step 5: Find out which factor pair sums up to $\color{blue}{ b = -25 }$
PRODUCT = 150 and SUM = -25 | |
1 150 | -1 -150 |
2 75 | -2 -75 |
3 50 | -3 -50 |
5 30 | -5 -30 |
6 25 | -6 -25 |
10 15 | -10 -15 |
Step 6: Replace middle term $ -25 x $ with $ -10x-15x $:
$$ 3x^{2}-25x+50 = 3x^{2}-10x-15x+50 $$Step 7: Apply factoring by grouping. Factor $ x $ out of the first two terms and $ -5 $ out of the last two terms.
$$ 3x^{2}-10x-15x+50 = x\left(3x-10\right) -5\left(3x-10\right) = \left(x-5\right) \left(3x-10\right) $$