Step 1 :
After factoring out $ 2 $ we have:
$$ 4x^{2}-70x+250 = 2 ( 2x^{2}-35x+125 ) $$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 $\color{blue}{ a = 2 }$ by the constant term $\color{blue}{c = 125} $.
$$ a \cdot c = 250 $$Step 4: Find out two numbers that multiply to $ a \cdot c = 250 $ and add to $ b = -35 $.
Step 5: All pairs of numbers with a product of $ 250 $ are:
PRODUCT = 250 | |
1 250 | -1 -250 |
2 125 | -2 -125 |
5 50 | -5 -50 |
10 25 | -10 -25 |
Step 6: Find out which factor pair sums up to $\color{blue}{ b = -35 }$
PRODUCT = 250 and SUM = -35 | |
1 250 | -1 -250 |
2 125 | -2 -125 |
5 50 | -5 -50 |
10 25 | -10 -25 |
Step 7: Replace middle term $ -35 x $ with $ -10x-25x $:
$$ 2x^{2}-35x+125 = 2x^{2}-10x-25x+125 $$Step 8: Apply factoring by grouping. Factor $ 2x $ out of the first two terms and $ -25 $ out of the last two terms.
$$ 2x^{2}-10x-25x+125 = 2x\left(x-5\right) -25\left(x-5\right) = \left(2x-25\right) \left(x-5\right) $$