Example

Example 7.26: Simplifying 1x+1yxyyx\frac{\frac{1}{x}+\frac{1}{y}}{\frac{x}{y}-\frac{y}{x}} by Writing it as Division

To simplify the complex rational expression 1x+1yxyyx\frac{\frac{1}{x}+\frac{1}{y}}{\frac{x}{y}-\frac{y}{x}} using division, apply the following procedure:

Step 1 — Simplify the numerator and denominator. In the numerator, the common denominator is xyxy. Multiplying 1x\frac{1}{x} by yy\frac{y}{y} and 1y\frac{1}{y} by xx\frac{x}{x} yields yxy+xxy=y+xxy\frac{y}{xy} + \frac{x}{xy} = \frac{y + x}{xy}. In the denominator, the common denominator is also xyxy. Multiplying xy\frac{x}{y} by xx\frac{x}{x} and yx\frac{y}{x} by yy\frac{y}{y} gives x2xyy2xy=x2y2xy\frac{x^2}{xy} - \frac{y^2}{xy} = \frac{x^2 - y^2}{xy}. The expression simplifies to y+xxyx2y2xy\frac{\frac{y + x}{xy}}{\frac{x^2 - y^2}{xy}}.

Step 2 — Rewrite as a division problem. The main fraction bar indicates division, so rewrite it as y+xxy÷x2y2xy\frac{y + x}{xy} \div \frac{x^2 - y^2}{xy}.

Step 3 — Multiply the first expression by the reciprocal of the second. Change the division to multiplication: y+xxyxyx2y2\frac{y + x}{xy} \cdot \frac{xy}{x^2 - y^2}.

Step 4 — Simplify. Factor the difference of squares in the denominator to (xy)(x+y)(x - y)(x + y). The expression becomes xy(y+x)xy(xy)(x+y)\frac{xy(y + x)}{xy(x - y)(x + y)}. Removing the common factors xyxy and (x+y)(x + y) (which is equivalent to (y+x)(y + x)) leaves 1xy\frac{1}{x - y}.

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Updated 2026-04-30

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