C^2-5c-14 (c-7)(c+2) c+2
----------- = ----------- = -----
c^2-6c-7 (c-7)(c+1) c+1
<span> x^4+x^2+1 = </span>x^4+2x^2+1-x^2= (x^2+1)^2 -x^2=( x^2+1 -x) (x^2+1+x);
x^4+4= x^4 +4x^2+4 -4x^2= (x^2+2)^2- 4x^2= (x^2+2 -2x) (x^2+2 +2x).
5x+y=24 x4
7x+4y=18
20x+4y=96 _
7x+4y=18
13x=78 5x6+y=24
x=6 y=-6