If it's not what You are looking for type in the equation solver your own equation and let us solve it.
D( z )
z = 0
z = 0
z = 0
z in (-oo:0) U (0:+oo)
4/z = 12/15 // - 12/15
4/z-(12/15) = 0
4/z-4/5 = 0
4*z^-1 = 4/5 // : 4
z^-1 = 1/5
-1 < 0
1/(z^1) = 1/5 // * z^1
1 = 1/5*z^1 // : 1/5
5 = z^1
z = 5
z = 5
| -4x-20=16-7x | | 5x-85=123-3x | | -14+10x=18+8x | | -4(x-8)=-20 | | 3/5=x/22 | | 3(5x-7)=25 | | 2x+4+6=x+14+1 | | 4x^2-16x+2.5=0 | | 8/9(x-1)=16 | | -3(x-5)-30=3 | | 8(2x+5)=6(x+10) | | n=r/2 | | 5(12x+2)=60x-3 | | 1.8+2.8=2.5+21 | | 8k^2+1=65 | | 7(3y-2)-(9y+5)= | | -30-10x=-12x+28 | | 3/10x=-15 | | -6=-(x-20) | | 12=-6-3/4x | | cosx=-0.09 | | 28x=7(10-x) | | 9x^2-5=31 | | 5y+3y=34-2 | | -7x-96=x-32 | | 27=-3x-5-5x | | 4x^2-36x-4=0 | | 10=2(x+2) | | (3a-2)x-a+3=x+8 | | -3v+6v=9+12 | | 12+6y=-6y | | V+13=8 |