Step 1 :
After factoring out $ -2 $ we have:
$$ -16t^{2}+34t-18 = -2 ( 8t^{2}-17t+9 ) $$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 $\color{blue}{ a = 8 }$ by the constant term $\color{blue}{c = 9} $.
$$ a \cdot c = 72 $$Step 4: Find out two numbers that multiply to $ a \cdot c = 72 $ and add to $ b = -17 $.
Step 5: All pairs of numbers with a product of $ 72 $ are:
PRODUCT = 72 | |
1 72 | -1 -72 |
2 36 | -2 -36 |
3 24 | -3 -24 |
4 18 | -4 -18 |
6 12 | -6 -12 |
8 9 | -8 -9 |
Step 6: Find out which factor pair sums up to $\color{blue}{ b = -17 }$
PRODUCT = 72 and SUM = -17 | |
1 72 | -1 -72 |
2 36 | -2 -36 |
3 24 | -3 -24 |
4 18 | -4 -18 |
6 12 | -6 -12 |
8 9 | -8 -9 |
Step 7: Replace middle term $ -17 x $ with $ -8x-9x $:
$$ 8x^{2}-17x+9 = 8x^{2}-8x-9x+9 $$Step 8: Apply factoring by grouping. Factor $ 8x $ out of the first two terms and $ -9 $ out of the last two terms.
$$ 8x^{2}-8x-9x+9 = 8x\left(x-1\right) -9\left(x-1\right) = \left(8x-9\right) \left(x-1\right) $$