Algebra · real student question

Add and simplify: (x + 5)/(2x − 2) + 3x/(x² + x − 2).

Question

Add and simplify

x+52x2+3xx2+x2\frac{x+5}{2x-2}+\frac{3x}{x^{2}+x-2}

Step-by-step solution

  1. Factor both denominators before choosing a common one. Multiplying the two denominators together would work but produces an unnecessarily large expression that must then be reduced. Factoring reveals the shared piece:

    2x2=2(x1),x2+x2=(x+2)(x1)2x-2=2(x-1),\qquad x^{2}+x-2=(x+2)(x-1)

  2. Build the least common denominator. Take each distinct factor to its highest power across the two denominators — the constant 22, the factor (x1)(x-1) that both share, and the factor (x+2)(x+2):

    LCD=2(x1)(x+2)\text{LCD}=2(x-1)(x+2)

  3. Rewrite each fraction over the LCD. The first needs an extra (x+2)(x+2); the second needs an extra 22:

    (x+5)(x+2)2(x1)(x+2)+23x2(x1)(x+2)\frac{(x+5)(x+2)}{2(x-1)(x+2)}+\frac{2\cdot 3x}{2(x-1)(x+2)}

  4. Add the numerators and collect.

    (x+5)(x+2)=x2+7x+10(x+5)(x+2)=x^{2}+7x+10

    x2+7x+10+6x=x2+13x+10x^{2}+7x+10+6x=x^{2}+13x+10

    so the sum is

    x2+13x+102(x1)(x+2)\frac{x^{2}+13x+10}{2(x-1)(x+2)}

  5. Check whether the result reduces. A cancellation would need x1x-1 or x+2x+2 to divide x2+13x+10x^2+13x+10. At x=1x=1 the numerator is 24024\neq 0; at x=2x=-2 it is 426+10=1204-26+10=-12\neq 0. Neither is a factor, so the expression is already in lowest terms.

    x2+13x+102(x1)(x+2)(x1, x2)\boxed{\dfrac{x^{2}+13x+10}{2(x-1)(x+2)}}\qquad (x\neq 1,\ x\neq -2)

  6. Verify with a test value. At x=3x=3: the original is 84+910=2+0.9=2.9\tfrac{8}{4}+\tfrac{9}{10}=2+0.9=2.9, and the answer gives 9+39+102(2)(5)=5820=2.9\tfrac{9+39+10}{2(2)(5)}=\tfrac{58}{20}=2.9. They agree.

Answer

x2+13x+102(x1)(x+2)\dfrac{x^{2}+13x+10}{2(x-1)(x+2)}

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