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Adding and Subtracting Rational Expression  Problem 1
Alissa Fong
Alissa Fong
MA, Stanford University
Teaching in the San Francisco Bay Area
Alissa is currently a teacher in the San Francisco Bay Area and Brightstorm users love her clear, concise explanations of tough concepts
These 2 rational expressions need to be added together, but I know it’s not going to be too bad because they already have common denominators. If I look both of these fractions already have x plus 2 in the bottom that means I know my sum is going to have x plus 2 in the bottom and all I need to do is look at the numerators or the tops.
It’s going to look like 3x² plus 6x. In order to simplify completely I’m going to factor the top and see if anything is going to cancel out and look my x plus 2 factors do cancel out, so my final sum is just going to be 3x.
The last thing I want to leave you with before you guys work on your homework problem though is that you have to consider excluded values. An excluded value remember is any value of x that would make this sum undefined, or what we mean by that is that would make this have a denominator of 0.
If I have the value x equals 2 that would mean my denominator would be 0 and in Math you guys know thou shall not divide by 0. 0 in the bottom of a fraction is what we call undefined. So I have the excluded value 2. I would write that as x cannot be 2 and I got that from looking at my original fractions, looking at the denominators and thinking about what values of x would make those denominators equal to 0.
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Alissa Fong
M.A. in Secondary Mathematics, Stanford University
B.S., Stanford University
Alissa has a quirky sense of humor and a relatable personality that make it easy for students to pay attention and understand the material. She has all the math tips and tricks students are looking for.
Sample Problems (6)
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Adding and Subtracting Rational Expression
Problem 1 7,457 viewsAdd and Simplify:
3x² + 6x x + 2 x + 2 
Adding and Subtracting Rational Expression
Problem 2 6,548 viewsSimplify:
7m − 2 − 5m − 6 m² + 3m + 2 m² + 3m + 2 
Adding and Subtracting Rational Expression
Problem 3 6,260 viewsSimplify:
4 + x² + x x + 3 x² + 4x + 3 
Adding and Subtracting Rational Expression
Problem 4 5,399 viewsSimplify:
x − x x² − 16 x² + 8x + 16 
Adding and Subtracting Rational Expression
Problem 5 781 views 
Adding and Subtracting Rational Expression
Problem 6 345 views
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