Question

Difficulty: MediumProperties of Exponents in Algebraic Expressions

For all real values of xx and yy where the expression is defined, simplify the algebraic fraction:

(x+y)3x2y(x+y)(xy1)2\frac{(x + y)^3 x^{-2} y}{(x+y) (x y^{-1})^{-2}}

Which expression is equivalent to this fraction?

  1. A
    x2+y2y\frac{x^2+y^2}{y}
  2. B
    (x+y)2y3\frac{(x+y)^2}{y^3}
  3. (x+y)2y\frac{(x+y)^2}{y}Answer
  4. D
    (x+y)^2 y^2
  5. E
    (x+y)2+2y+2\frac{(x+y)^2 + 2}{y+2}

Answer

The expression (x+y)2y\frac{(x+y)^2}{y}
The correct expression is derived by first simplifying the denominator (xy1)2(xy^{-1})^{-2} to x2y2x^{-2}y^2. We then group and simplify like terms: (x+y)3x+y=(x+y)2\frac{(x+y)^3}{x+y} = (x+y)^2, x2x2=1\frac{x^{-2}}{x^{-2}} = 1, and yy2=1y\frac{y}{y^2} = \frac{1}{y}. Multiplying these yields the simplified expression.

Step-by-Step Solution

1
Simplify the term (xy1)2(x y^{-1})^{-2} in the denominator
x2y2x^{-2} y^2
Apply the power of a product rule: (ab)n=anbn(ab)^n = a^n b^n, which gives x2(y1)2x^{-2} (y^{-1})^{-2}. Then, use the power of a power rule: (y1)2=y(1)(2)=y2(y^{-1})^{-2} = y^{(-1) \cdot (-2)} = y^2.
2
Rewrite the original fraction with the simplified denominator
(x+y)3x2y(x+y)x2y2\frac{(x + y)^3 x^{-2} y}{(x+y) x^{-2} y^2}
Substitute the simplified term back into the expression to align similar bases.
3
Simplify the fraction by dividing terms with like bases using the quotient rule
(x+y)2y\frac{(x+y)^2}{y}
Divide each component: (x+y)3x+y=(x+y)31=(x+y)2\frac{(x+y)^3}{x+y} = (x+y)^{3-1} = (x+y)^2, x2x2=x2(2)=x0=1\frac{x^{-2}}{x^{-2}} = x^{-2 - (-2)} = x^0 = 1, and yy2=y12=y1=1y\frac{y}{y^2} = y^{1-2} = y^{-1} = \frac{1}{y}. Multiplying these results gives (x+y)2y\frac{(x+y)^2}{y}.

Key Concept

Properties of exponents in algebraic expressions, including power of a product, power of a power, and quotient rules.
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