Step 1 :
After factoring out $ 7 $ we have:
$$ 14z^{2}-49z+35 = 7 ( 2z^{2}-7z+5 ) $$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 = 5} $.
$$ a \cdot c = 10 $$Step 4: Find out two numbers that multiply to $ a \cdot c = 10 $ and add to $ b = -7 $.
Step 5: All pairs of numbers with a product of $ 10 $ are:
PRODUCT = 10 | |
1 10 | -1 -10 |
2 5 | -2 -5 |
Step 6: Find out which factor pair sums up to $\color{blue}{ b = -7 }$
PRODUCT = 10 and SUM = -7 | |
1 10 | -1 -10 |
2 5 | -2 -5 |
Step 7: Replace middle term $ -7 x $ with $ -2x-5x $:
$$ 2x^{2}-7x+5 = 2x^{2}-2x-5x+5 $$Step 8: Apply factoring by grouping. Factor $ 2x $ out of the first two terms and $ -5 $ out of the last two terms.
$$ 2x^{2}-2x-5x+5 = 2x\left(x-1\right) -5\left(x-1\right) = \left(2x-5\right) \left(x-1\right) $$