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Math Grade 9-12 Answer Key

Rational Expressions and Equations

Simplifying, combining, and solving with rational expressions

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Rational Expressions and Equations

Simplifying, combining, and solving with rational expressions

Math - Grade 9-12

Instructions: Read each problem carefully. Simplify all answers when possible, and state any values that make an expression undefined.
  1. 1

    Simplify the expression (6x)/(9).

    Reduce the numerical fraction first.

    The expression simplifies to 2x/3.
  2. 2

    Simplify the rational expression (x^2 - 9)/(x + 3). State any restriction on x.

    Factor the numerator as a difference of squares.

    The expression simplifies to x - 3, with the restriction x does not equal -3.
  3. 3

    Simplify the rational expression (x^2 + 5x)/(x). State any restriction on x.

    The expression simplifies to x + 5, with the restriction x does not equal 0.
  4. 4

    Multiply and simplify: (2/x) · (3x/5). State any restriction on x.

    Cancel common factors before multiplying.

    The product simplifies to 6/5, with the restriction x does not equal 0.
  5. 5

    Divide and simplify: (4/x) ÷ (2/x^2). State any restriction on x.

    The quotient simplifies to 2x, with the restriction x does not equal 0.
  6. 6

    Add and simplify: 3/x + 2/x.

    The sum simplifies to 5/x, with the restriction x does not equal 0.
  7. 7

    Add and simplify: 1/x + 1/2. State any restriction on x.

    Find a common denominator of 2x.

    The sum simplifies to (x + 2)/(2x), with the restriction x does not equal 0.
  8. 8

    Subtract and simplify: 5/(x + 1) - 2/(x + 1). State any restriction on x.

    The difference simplifies to 3/(x + 1), with the restriction x does not equal -1.
  9. 9

    Simplify the complex fraction (1/x) / (2/3). State any restriction on x.

    Dividing by a fraction means multiplying by its reciprocal.

    The expression simplifies to 3/(2x), with the restriction x does not equal 0.
  10. 10

    State all values of x that make the expression (x + 4)/(x^2 - 16) undefined.

    The expression is undefined when x equals 4 or x equals -4 because those values make the denominator zero.
  11. 11

    Solve the rational equation 3/x = 12.

    Multiply both sides by x, then divide by 12.

    The solution is x = 1/4.
  12. 12

    Solve the rational equation x/(x + 2) = 3/4. State any restricted value.

    The solution is x = 6, with the restriction x does not equal -2.
  13. 13

    Solve the rational equation 2/(x - 1) = 1. State any restricted value.

    Multiply both sides by x - 1.

    The solution is x = 3, with the restriction x does not equal 1.
  14. 14

    Solve the rational equation 1/x + 1/x = 1. State any restricted value.

    Combining the left side gives 2/x = 1, so the solution is x = 2, with the restriction x does not equal 0.
  15. 15

    A rectangle has area 24 square units and width x units. Write and simplify a rational expression for the length of the rectangle in terms of x. State any restriction on x.

    Use area = length × width.

    The length is 24/x units, with the restriction x does not equal 0.
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