Question 83342
what is the sum of:
x+1 and 3x
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x+3    x-4

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to add the fractions they must have a common denominator:
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lcm = (x+3)(x-4)
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[(x+1)(x-4)] /lcm + (3x(x+3)/lcm

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Now add the numerators to get:

= [x^2-3x-4+3x^2+9x]/lcm

= [4x^2+6x-4]/[x^2+x-12]

= [2(2x+3x-2)]/[(x+3)(x-4)]
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Cheers,
Stan H.