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How do you factor a binomial

Ex. 30y^3 - 50y

 May 18, 2014

Best Answer 

 #1
avatar+6251 
+8

find all the common factors and bring them to the front of the expression.

In this case 10y is a common factor.

$$30y^3-50y=10y\left(3y^2-5\right)$$

it should be fine to stop there, but if you want to go nuts you can do this.

$$30y^3-50y=30y\left(y^2-\frac 5 3\right)=30y\left(y-\sqrt{\frac 5 3}\right)\left(y+\sqrt{\frac 5 3}\right)$$

 May 19, 2014
 #1
avatar+6251 
+8
Best Answer

find all the common factors and bring them to the front of the expression.

In this case 10y is a common factor.

$$30y^3-50y=10y\left(3y^2-5\right)$$

it should be fine to stop there, but if you want to go nuts you can do this.

$$30y^3-50y=30y\left(y^2-\frac 5 3\right)=30y\left(y-\sqrt{\frac 5 3}\right)\left(y+\sqrt{\frac 5 3}\right)$$

Rom May 19, 2014
 #2
avatar+129847 
+5

I used to use that second form of factoring, too, Rom. It drove my teachers crazy!! I asked them why a radical wasn't just as valid as an integer in a factored expression since they were both "real" numbers......They use to say, "Because you can't do that." I told them, "But, I just did!!"

 May 19, 2014
 #3
avatar+118667 
+5

Yes, and I don't see why it is not used on more complicated ones as well!  

I lost my sunnies - never mind IO found them again!  

 May 19, 2014

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