Algebra - Subtract Fraction with X?

[7(4x + 12) - 5(3x + 9)]/(3x + 9)(4x + 12)

=> (13x + 39)/12(x + 3)(x + 3)

=> 13(x + 3)/12(x + 3)(x + 3)

i.e. 13/12(x + 3)

:)>

Well first factor out the denominators as much as possible:

(7) / 3(x + 3) - (5) / 4(x + 3)

Multiply the first fraction by 4/4 and the second fraction by 3/3 to make the denominators common:

(28) / 12(x + 3) - (15) / 12(x + 3)

Now that the denominators are common, expand the numerators and combine them:

(28) - (15)

28 - 15

= 13/12(x + 3)

That can not be simplified any further.

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It's very easy to check your solutions as well, just give x any value (it doesn't matter what it is, as long as it doesn't involve division by zero), and the result should be exactly the same as the question.

x = 1

7/12 - 5/16

= 13/48

13/12(4)

= 13/48

They are equal!

is this what you're after? 5m/(m+a million)+(a million+4m)/(m+a million)=(m-a million)/(m+a million) multiply the two sides with the aid of (m+a million) and get: 5m + (a million+4m) = m-a million 9m +a million=m-a million 8m=-2 m=-a million/4 (a+b)/2 + (a-b)/2 = b multiply the two sides with the aid of 2 and get: a+b + a-b = 2b 2a = 2b a = b x^2/(x+5) - 5x/(x+5) = x multiply the two sides with the aid of (x=5) to get: x^2 -5x = x(x+5) x^2 - 5x = x^2 + 5x -5x = 5x x = -x x subsequently could be 0