Step 1 :
After factoring out $ 5 $ we have:
$$ 15s^{2}+50s+15 = 5 ( 3s^{2}+10s+3 ) $$Step 2 :
Step 2: 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 3: Multiply the leading coefficient $\color{blue}{ a = 3 }$ by the constant term $\color{blue}{c = 3} $.
$$ a \cdot c = 9 $$Step 4: Find out two numbers that multiply to $ a \cdot c = 9 $ and add to $ b = 10 $.
Step 5: All pairs of numbers with a product of $ 9 $ are:
PRODUCT = 9 | |
1 9 | -1 -9 |
3 3 | -3 -3 |
Step 6: Find out which factor pair sums up to $\color{blue}{ b = 10 }$
PRODUCT = 9 and SUM = 10 | |
1 9 | -1 -9 |
3 3 | -3 -3 |
Step 7: Replace middle term $ 10 x $ with $ 9x+x $:
$$ 3x^{2}+10x+3 = 3x^{2}+9x+x+3 $$Step 8: Apply factoring by grouping. Factor $ 3x $ out of the first two terms and $ 1 $ out of the last two terms.
$$ 3x^{2}+9x+x+3 = 3x\left(x+3\right) + 1\left(x+3\right) = \left(3x+1\right) \left(x+3\right) $$