If it's not what You are looking for type in the equation solver your own equation and let us solve it.
D( x )
x = 0
7*x-21 = 0
x = 0
x = 0
7*x-21 = 0
7*x-21 = 0
7*x-21 = 0 // + 21
7*x = 21 // : 7
x = 21/7
x = 3
x in (-oo:0) U (0:3) U (3:+oo)
1/x+1/x-7 = 15/(7*x-21) // - 15/(7*x-21)
1/x-(15/(7*x-21))+1/x-7 = 0
1/x-15*(7*x-21)^-1+1/x-7 = 0
1/x-15/(7*x-21)+1/x-7 = 0
(-15*x)/(x*(7*x-21))+(1*(7*x-21))/(x*(7*x-21))+(1*(7*x-21))/(x*(7*x-21))+(-7*x*(7*x-21))/(x*(7*x-21)) = 0
1*(7*x-21)+1*(7*x-21)-7*x*(7*x-21)-15*x = 0
7*x-49*x^2-8*x+147*x-21-21 = 0
147*x-49*x^2-x-42 = 0
146*x-49*x^2-42 = 0
146*x-49*x^2-42 = 0
146*x-49*x^2-42 = 0
DELTA = 146^2-(-49*(-42)*4)
DELTA = 13084
DELTA > 0
x = (13084^(1/2)-146)/(-49*2) or x = (-13084^(1/2)-146)/(-49*2)
x = (2*3271^(1/2)-146)/(-98) or x = (-2*3271^(1/2)-146)/(-98)
(x-((2*3271^(1/2)-146)/(-98)))*(x-((-2*3271^(1/2)-146)/(-98))) = 0
((x-((2*3271^(1/2)-146)/(-98)))*(x-((-2*3271^(1/2)-146)/(-98))))/(x*(7*x-21)) = 0
((x-((2*3271^(1/2)-146)/(-98)))*(x-((-2*3271^(1/2)-146)/(-98))))/(x*(7*x-21)) = 0 // * x*(7*x-21)
(x-((2*3271^(1/2)-146)/(-98)))*(x-((-2*3271^(1/2)-146)/(-98))) = 0
( x-((-2*3271^(1/2)-146)/(-98)) )
x-((-2*3271^(1/2)-146)/(-98)) = 0 // + (-2*3271^(1/2)-146)/(-98)
x = (-2*3271^(1/2)-146)/(-98)
( x-((2*3271^(1/2)-146)/(-98)) )
x-((2*3271^(1/2)-146)/(-98)) = 0 // + (2*3271^(1/2)-146)/(-98)
x = (2*3271^(1/2)-146)/(-98)
x in { (-2*3271^(1/2)-146)/(-98), (2*3271^(1/2)-146)/(-98) }
| X=0.5-6 | | 3.2x+8.3=1.3x+1937 | | (3x+30)=90 | | -21+23=m-7 | | 432/(-18)/(-3) | | x+4x+2+2x-6=10 | | 11-6/b=23 | | x(2x-8)=(2x+7)(x+6) | | 3(x+4)=12+6x-6 | | (1/x)+(1/x-9)=(19)/(9x-33) | | -10=20-6 | | 5(x+5)+3(x-2)=3 | | (x+1)/(2x-1)=(4x-3)/(2x+1) | | 3x+15=51 | | 18-7X=6-4X | | x^4-9x^3=81x^2-729x | | -6(x-3)=24 | | 2(3x+4)=-4+4x+10 | | 5(5t-2)+10=-25 | | 2+4(-2d-3)=14 | | -7a+3a-3=0 | | 6(-4x-5)=66 | | 3-x=4x+2 | | 6y+18=2x+18 | | (7x-11)= | | -10-4x+7x=20 | | 7xh=3-5xh | | -64=3x+4x+3 | | -2x+10+x+3=4 | | -6x-4+2x=-4 | | -2(1x+5)=-18 | | 8-8*6/4+9 |