# Simplify without changing the denominator

I have the following expression:

    1/2 (-c y - 2/((2 + x) (1 - δ)) + (
2 (1 + y))/((2 + x + y) (1 - δ))) +
1/4 (-c x - c y +
1/4 (1/(1 - δ) - (2 (1 + x))/((2 + x) (1 - δ))) +
1/4 (1/2 (c x + 1/(1 - δ) - (
2 (1 + x))/((2 + x) (1 - δ))) +
1/2 (c y + 1/(1 - δ) - (
2 (1 + y))/((2 + y) (1 - δ))) - 2/(1 - δ) -
2/((2 + x) (1 - δ)) - 2/((2 + y) (1 - δ))) +
1/4 (1/2 (-c x - 1/(1 - δ) + (
2 (1 + x))/((2 + x) (1 - δ))) +
1/2 (-c y - 1/(1 - δ) + (
2 (1 + y))/((2 + y) (1 - δ))) + 2/(1 - δ) +
2/((2 + x) (1 - δ)) + 2/((2 + y) (1 - δ))) + (
2 (1 + x))/((2 + x + y) (1 - δ)) + (
2 (1 + y))/((2 + x + y) (1 - δ)))


I want to simplify without changing the denominator. For example, you see that the terms:

-c y; -c x


appears many times. Also the term:

/((2 + x + y)


Also appear many times. I want to simplify those, by taking out. For example:

1/2 (-c y - 2/((2 + x) (1 - δ)) + 1/4 (-c x - c y)


when simplify, my desired result would have:

-3/4 c y


How to do that? If I just use simplify for the entire thing, the result will be:

-((8 (4 + y (4 + 6 c (-1 + δ)) + 3 c y^2 (-1 + δ)) +
x^2 (7 + 16 c (1 + y) (-1 + δ)) +
x (30 + 23 y + 4 c (4 + 14 y + 3 y^2) (-1 + δ)) +
4 c x^3 (-1 + δ))/(16 (2 + x) (2 + x + y) (-1 + δ)))


Which I do not want.

• Have you tried separating your fraction into its numerator and denominator, simplifying the numerator, then reconstituting the fraction? You could perhaps use NumeratorDenominator to get the two, then only Simplify the first. – MarcoB Jan 22 '20 at 13:24
• I used Expand and got what I needed – user66418 Feb 25 '20 at 1:51