PSAT Math : How to add rational expressions with a common denominator

Study concepts, example questions & explanations for PSAT Math

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Example Questions

Example Question #41 : Expressions

Simplify. 

Possible Answers:

Correct answer:

Explanation:

Same denominator means you add straight across the numerators, keeping the denominator the same.

Add like terms. 

Final Answer. 

Example Question #42 : Expressions

Simplify.

Possible Answers:

Correct answer:

Explanation:

Check for same Denominator

Add like terms 

Check for GCF or if the expression can be factored

After factoring, divide out like terms. 

Final Answer

Example Question #11 : Rational Expressions

Simplify the following rational expression: (9x - 2)/(x2) MINUS (6x - 8)/(x2)

Possible Answers:

Correct answer:

Explanation:

Since both expressions have a common denominator, x2, we can just recopy the denominator and focus on the numerators. We get (9x - 2) - (6x - 8). We must distribute the negative sign over the 6x - 8 expression which gives us 9x - 2 - 6x + 8 ( -2 minus a -8 gives a +6 since a negative and negative make a positive). The numerator is therefore 3x + 6.

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