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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.
Your tutorials are good and you have a personality as well. I hope you have more advanced college level stuff, because I like the way you teach.”
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Sample Problems (6)
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Adding and Subtracting Rational Expression
Problem 1 7,210 viewsAdd and Simplify:
3x² + 6x x + 2 x + 2 
Adding and Subtracting Rational Expression
Problem 2 6,244 viewsSimplify:
7m − 2 − 5m − 6 m² + 3m + 2 m² + 3m + 2 
Adding and Subtracting Rational Expression
Problem 3 5,982 viewsSimplify:
4 + x² + x x + 3 x² + 4x + 3 
Adding and Subtracting Rational Expression
Problem 4 5,151 viewsSimplify:
x − x x² − 16 x² + 8x + 16 
Adding and Subtracting Rational Expression
Problem 5 641 views 
Adding and Subtracting Rational Expression
Problem 6 243 views
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