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QUESTION IMAGE

addition and subtraction of rational expressions with different denomin…

Question

addition and subtraction of rational expressions with different denominators involve converting each expression into equivalent rational expressions with the least common denominator.
\\(\frac{3}{x - 5} + \frac{x}{x + 2}\\)
\\(\frac{m}{m + 3} - \frac{2}{m - 1}\\)
\\(\frac{4 - 2p}{p^2 - p - 2} + \frac{p + 2}{p + 1}\\)
\\(\frac{4 - a}{a - 3} - \frac{a - 3}{a^2 - 6a + 9}\\)
\\(\frac{3}{u^2 + 7u + 10} - \frac{2}{u^2 + 8u + 15}\\)
\\(\frac{1}{n^2 - 1} + \frac{3}{n^2 - 4n + 3}\\)
\\(\frac{8}{y + 9} - \frac{9}{3y + 27}\\)
\\(\frac{1}{b + 1} + \frac{2}{b^2 - 1}\\)
\\(\frac{10}{x - 5} - \frac{2x^2 + 4x}{x^2 - 3x - 10}\\)

Explanation:

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1. $\boldsymbol{\frac{3}{x-5} + \frac{x}{x+2}}$

Step1: Find common denominator

Least common denominator is $(x-5)(x+2)$

Step2: Rewrite each fraction

$\frac{3(x+2)}{(x-5)(x+2)} + \frac{x(x-5)}{(x-5)(x+2)}$

Step3: Combine numerators

$\frac{3(x+2) + x(x-5)}{(x-5)(x+2)}$

Step4: Expand and simplify numerator

$\frac{3x+6 + x^2 -5x}{(x-5)(x+2)} = \frac{x^2 -2x +6}{(x-5)(x+2)}$

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2. $\boldsymbol{\frac{m}{m+3} - \frac{2}{m-1}}$

Step1: Find common denominator

Least common denominator is $(m+3)(m-1)$

Step2: Rewrite each fraction

$\frac{m(m-1)}{(m+3)(m-1)} - \frac{2(m+3)}{(m+3)(m-1)}$

Step3: Combine numerators

$\frac{m(m-1) - 2(m+3)}{(m+3)(m-1)}$

Step4: Expand and simplify numerator

$\frac{m^2 -m -2m -6}{(m+3)(m-1)} = \frac{m^2 -3m -6}{(m+3)(m-1)}$

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3. $\boldsymbol{\frac{4-2p}{p^2-p-2} + \frac{p+2}{p+1}}$

Step1: Factor denominator

$p^2-p-2=(p-2)(p+1)$

Step2: Find common denominator

Least common denominator is $(p-2)(p+1)$

Step3: Rewrite second fraction

$\frac{4-2p}{(p-2)(p+1)} + \frac{(p+2)(p-2)}{(p-2)(p+1)}$

Step4: Factor $4-2p$

$\frac{-2(p-2)}{(p-2)(p+1)} + \frac{(p+2)(p-2)}{(p-2)(p+1)}$

Step5: Combine numerators

$\frac{-2(p-2) + (p+2)(p-2)}{(p-2)(p+1)}$

Step6: Factor numerator, cancel terms

$\frac{(p-2)(-2 + p + 2)}{(p-2)(p+1)} = \frac{p}{p+1}$ (where $p
eq 2$)

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4. $\boldsymbol{\frac{4-a}{a-3} - \frac{a-3}{a^2-6a+9}}$

Step1: Factor denominator

$a^2-6a+9=(a-3)^2$

Step2: Find common denominator

Least common denominator is $(a-3)^2$

Step3: Rewrite first fraction

$\frac{(4-a)(a-3)}{(a-3)^2} - \frac{a-3}{(a-3)^2}$

Step4: Combine numerators

$\frac{(4-a)(a-3) - (a-3)}{(a-3)^2}$

Step5: Factor numerator, cancel terms

$\frac{(a-3)(4-a -1)}{(a-3)^2} = \frac{3-a}{a-3} = -1$ (where $a
eq 3$)

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5. $\boldsymbol{\frac{3}{u^2+7u+10} - \frac{2}{u^2+8u+15}}$

Step1: Factor denominators

$u^2+7u+10=(u+2)(u+5)$; $u^2+8u+15=(u+3)(u+5)$

Step2: Find common denominator

Least common denominator is $(u+2)(u+3)(u+5)$

Step3: Rewrite each fraction

$\frac{3(u+3)}{(u+2)(u+3)(u+5)} - \frac{2(u+2)}{(u+2)(u+3)(u+5)}$

Step4: Combine numerators

$\frac{3(u+3) - 2(u+2)}{(u+2)(u+3)(u+5)}$

Step5: Simplify numerator

$\frac{3u+9-2u-4}{(u+2)(u+3)(u+5)} = \frac{u+5}{(u+2)(u+3)(u+5)} = \frac{1}{(u+2)(u+3)}$ (where $u
eq -5$)

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6. $\boldsymbol{\frac{1}{n^2-1} + \frac{3}{n^2-4n+3}}$

Step1: Factor denominators

$n^2-1=(n-1)(n+1)$; $n^2-4n+3=(n-1)(n-3)$

Step2: Find common denominator

Least common denominator is $(n-1)(n+1)(n-3)$

Step3: Rewrite each fraction

$\frac{n-3}{(n-1)(n+1)(n-3)} + \frac{3(n+1)}{(n-1)(n+1)(n-3)}$

Step4: Combine numerators

$\frac{n-3 + 3(n+1)}{(n-1)(n+1)(n-3)}$

Step5: Simplify numerator

$\frac{n-3+3n+3}{(n-1)(n+1)(n-3)} = \frac{4n}{(n-1)(n+1)(n-3)}$

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7. $\boldsymbol{\frac{8}{y+9} - \frac{9}{3y+27}}$

Step1: Factor second denominator

$3y+27=3(y+9)$

Step2: Find common denominator

Least common denominator is $3(y+9)$

Step3: Rewrite first fraction

$\frac{8 \cdot 3}{3(y+9)} - \frac{9}{3(y+9)}$

Step4: Combine numerators

$\frac{24 - 9}{3(y+9)} = \frac{15}{3(y+9)} = \frac{5}{y+9}$

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8. $\boldsymbol{\frac{1}{b+1} + \frac{2}{b^2-1}}$

Step1: Factor second denominator

$b^2-1=(b-1)(b+1)$

Step2: Find common denominator

Least common denominator is $(b-1)(b+1)$

Step3: Rewrite first fraction

$\frac{b-1}{(b-1)(b+1)} + \frac{2}{(b-1)(b+1)}$

Step4: Combine numerators

$\frac{b-1 + 2}{(b-1)(b+1)} = \frac{b+1}{(b-1)(b+1)} = \frac{1}{b-1}$ (where $b
eq -1$)

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9. $\boldsymbol{\frac{10}{x-5} - \frac{2x^2+4x}{x^2-3x-1…

Answer:

  1. $\boldsymbol{\frac{x^2 -2x +6}{(x-5)(x+2)}}$
  2. $\boldsymbol{\frac{m^2 -3m -6}{(m+3)(m-1)}}$
  3. $\boldsymbol{\frac{p}{p+1}}$ (for $p

eq 2$)

  1. $\boldsymbol{-1}$ (for $a

eq 3$)

  1. $\boldsymbol{\frac{1}{(u+2)(u+3)}}$ (for $u

eq -5$)

  1. $\boldsymbol{\frac{4n}{(n-1)(n+1)(n-3)}}$
  2. $\boldsymbol{\frac{5}{y+9}}$
  3. $\boldsymbol{\frac{1}{b-1}}$ (for $b

eq -1$)

  1. $\boldsymbol{-2}$ (for $x

eq -2, 5$)