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Solution 2.1:1d

From Förberedande kurs i matematik 1

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Current revision (07:48, 23 September 2008) (edit) (undo)
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After <math> x^3y^2 </math> are multiplied inside the bracket, we can eliminate factors which occur in both the numerator and denominator,
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<center> [[Bild:2_1_1d.gif]] </center>
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{{Displayed math||<math>\begin{align}
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x^3y^2\Big( \frac{1}{y} - \frac{1}{xy} +1 \Big) &= x^3y^2 \cdot\frac{1}{y} -x^3y^2 \cdot \frac{1}{xy} +x^3y^2\cdot 1 \\
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&=\frac{x^3y^2}{y} -\frac{x^3y^2}{xy} +x^3y^2 \\
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&=x^3y - x^2y +x^3y^2\,,
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\end{align}</math>}}
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where we have used
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{{Displayed math||<math>\begin{align}
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\frac{x^3y^2}{y} &= \frac{x^3\cdot y\cdot{}\rlap{/}y}{\rlap{/}y}= x^3y\,,\\[5pt]
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\frac{x^3y^2}{xy} &= \frac{\rlap{/}x\cdot x\cdot x \cdot y \cdot {}\rlap{/}y}{\rlap{/}x\cdot {}\rlap{/}y} = x\cdot x\cdot y = x^2y\,\textrm{.}\end{align}</math>}}

Current revision

After x3y2 are multiplied inside the bracket, we can eliminate factors which occur in both the numerator and denominator,

x3y2y11xy+1=x3y2y1x3y21xy+x3y21=yx3y2xyx3y2+x3y2=x3yx2y+x3y2

where we have used

yx3y2xyx3y2=yx3yy=x3y=xyxxxyy=xxy=x2y.