Factor polynomial $$ 21y^{3}-6y^{2}+15y $$

$$ 21y^{3}-6y^{2}+15y = 3y( 7y^{2}-2y+5 ) $$

Step 1 :

After factoring out $ 3y $ we have:

$$ 21y^{3}-6y^{2}+15y = 3y ( 7y^{2}-2y+5 ) $$

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:

$$ a = 7 , b = -2 ~ \text{ and } ~ c = 5 $$

Step 3: Multiply the leading coefficient $\color{blue}{ a = 7 }$ by the constant term $\color{blue}{c = 5} $.

$$ a \cdot c = 35 $$

Step 4: Find out two numbers that multiply to $ a \cdot c = 35 $ and add to $ b = -2 $.

Step 5: All pairs of numbers with a product of $ 35 $ are:

PRODUCT = 35
1     35	-1     -35
5     7	-5     -7

Step 6: Find out which factor pair sums up to $\color{blue}{ b = -2 }$

Step 7: Because none of these pairs will give us a sum of $ \color{blue}{ -2 }$, we conclude the polynomial cannot be factored.

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