Maths-
General
Easy

Question

What is the simplified form of the rational expression fraction numerator x squared minus 36 over denominator x squared plus 3 x minus 18 end fraction ? What is its domain?

The correct answer is: The domain of the expression is the set of values excluding the zero value of the denominator. That is: x - 3 = 0 x = 3


    ANSWER:
    Hint:
    The expansions of certain identities are:
    open parentheses x squared minus a squared close parentheses equals left parenthesis x minus a right parenthesis left parenthesis x plus a right parenthesis
    x squared plus left parenthesis a plus b right parenthesis x plus a b equals left parenthesis x plus a right parenthesis left parenthesis x plus b right parenthesis
    We are asked to simplify the expression and find its domain.
    Step 2 of 3:
    Simplify the denominator of the expression:
    fraction numerator x squared minus 36 over denominator x squared plus 3 x minus 18 end fraction equals fraction numerator x squared minus 6 squared over denominator x squared plus 3 x minus 18 end fraction
    equals fraction numerator left parenthesis x minus 6 right parenthesis left parenthesis x plus 6 right parenthesis over denominator x squared plus 3 x minus 18 end fraction
    Step 2 of 3:
    Simplify the denominator of the expression:
    fraction numerator left parenthesis x minus 6 right parenthesis left parenthesis x plus 6 right parenthesis over denominator x squared plus 3 x minus 18 end fraction equals fraction numerator left parenthesis x minus 6 right parenthesis left parenthesis x plus 6 right parenthesis over denominator x squared plus 6 x minus 3 x minus 18 end fraction
    equals fraction numerator left parenthesis x minus 6 right parenthesis left parenthesis x plus 6 right parenthesis over denominator x left parenthesis x plus 6 right parenthesis minus 3 left parenthesis x plus 6 right parenthesis end fraction
    equals fraction numerator left parenthesis x minus 6 right parenthesis left parenthesis x plus 6 right parenthesis over denominator left parenthesis x minus 3 right parenthesis left parenthesis x plus 6 right parenthesis end fraction
    equals fraction numerator x minus 6 over denominator x minus 3 end fraction
    Step 3 of 3:
    The domain of the expression is the set of values excluding the zero value of the denominator. That is:
    x minus 3 equals 0
    x equals 3
    Hence, the domain is:left parenthesis negative straight infinity comma 3 right parenthesis union left parenthesis 3 comma straight infinity right parenthesis
    Note:
    When you find the domain of a rational expression exclude the values that bring zero to the denominator.
     

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