If it's not what You are looking for type in the equation solver your own equation and let us solve it.
D( n )
n = 0
n = 0
n = 0
n in (-oo:0) U (0:+oo)
105/15 = 21/n // - 21/n
105/15-(21/n) = 0
105/15-21*n^-1 = 0
-21*n^-1 = -7 // : -21
n^-1 = 1/3
-1 < 0
1/(n^1) = 1/3 // * n^1
1 = 1/3*n^1 // : 1/3
3 = n^1
n = 3
n = 3
| 15y+50=5y+90 | | 2x+7=193 | | 3x+35=23 | | x^2+5x+9=9x+8 | | 10x+.10=15 | | .80x+14.40=254.40 | | 14.40x+.8=254.40 | | 2.2r+.47=1.79 | | -1*7+2=2+-1*7 | | 8y+11=63 | | (3y)+(2y+2)=48 | | .13x+.07=.551 | | .8d+.2=.76 | | 2x-22=16-7+8x | | 1.1w+2.1=5.4 | | y=30000+500x | | 10y+12x=360 | | 6+5x=37 | | 3[6-(-5x-2)]=60x+42 | | 4x^2-8x-172=0 | | (18x-9)+(4x+13)= | | 10-0.75x=7 | | 2(t-2)-3(2t-3)=5-5(3t+2) | | 2x+3(8-3x)=3 | | 3x^4-13x^2+1=0 | | x^2*7b=0 | | x^7*b=0 | | X+4(9)=16 | | 5-7+2*10= | | 9/4T=3/16 | | 0.25x+6=.66x+28 | | .09x+4= |