a. Show that the system of rational expressions is closed under addition, or give an example showing the contrary.

1 answer:

7 0

A "rational expression" is a fraction in which the numerator and the denominator are both polynomials. The sum of two such expressions will always produce another such expression, viz.,
p(x)/q(x) + r(x)/s(x) = [p(x)s(x) + q(x)r(x)] / [q(x)*s(x)]. 
The numerator and denominator of the sum will both be polynomials when fully expanded

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weeeeeb [17]

Answer:

O is the center of the circle with radius IE(=ID=EF)

Step-by-step explanation:

Join all 3 points D, E, F, forming the triangle DEF.

Let the midpoint of EF be M and the midpoint of ED be N. (first picture)

Join point I to E, D and F.

Since IN is both an altitude and median to triangle EID, then triangle EID is an isosceles triangle, and IE=ID

similarly, we see that IE=IF.

conclusion: IE=ID=EF.