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
x = 0
x = 0
x in (-oo:0) U (0:+oo)
((180*x-1800)/x)*(x-20) = 4 // - 4
((180*x-1800)/x)*(x-20)-4 = 0
((180*x-1800)*(x-20))/x-4 = 0
((180*x-1800)*(x-20))/x+(-4*x)/x = 0
(180*x-1800)*(x-20)-4*x = 0
180*x^2-5404*x+36000 = 0
180*x^2-5404*x+36000 = 0
4*(45*x^2-1351*x+9000) = 0
45*x^2-1351*x+9000 = 0
DELTA = (-1351)^2-(4*45*9000)
DELTA = 205201
DELTA > 0
x = (205201^(1/2)+1351)/(2*45) or x = (1351-205201^(1/2))/(2*45)
x = (205201^(1/2)+1351)/90 or x = (1351-205201^(1/2))/90
4*(x-((1351-205201^(1/2))/90))*(x-((205201^(1/2)+1351)/90)) = 0
(4*(x-((1351-205201^(1/2))/90))*(x-((205201^(1/2)+1351)/90)))/x = 0
(4*(x-((1351-205201^(1/2))/90))*(x-((205201^(1/2)+1351)/90)))/x = 0 // * x
4*(x-((1351-205201^(1/2))/90))*(x-((205201^(1/2)+1351)/90)) = 0
( x-((1351-205201^(1/2))/90) )
x-((1351-205201^(1/2))/90) = 0 // + (1351-205201^(1/2))/90
x = (1351-205201^(1/2))/90
( x-((205201^(1/2)+1351)/90) )
x-((205201^(1/2)+1351)/90) = 0 // + (205201^(1/2)+1351)/90
x = (205201^(1/2)+1351)/90
x in { (1351-205201^(1/2))/90, (205201^(1/2)+1351)/90 }
| (3z+5)(2z+7)= | | c=hp | | x=75+3t | | s/r-q/r=1 | | (3z+5)*(2z+7)= | | 2(x-5)+3(x+4)=x(-6)+2 | | 4d^2+19d^2-5=0 | | 16-4x=7-7x | | 9ab+a+a= | | 10=4x+(1-x)13.125 | | 15=9e | | 9=4x+(1-x)21 | | 2x=6x-24 | | (4x-6)+(3x-2)+x=y | | 110=r*22 | | 10.5a+6c=6000 | | 10.5+6c=6000 | | 12.28/2.6=5.2/n | | 4a^3+3a^2b^2+8a+6b^2=0 | | d=78 | | 0.375=x+ln(x-0.2) | | 3(2x+4)=4(5x-4) | | -13-(-42)=x/4 | | 7-4(9+2)=9+9 | | 2(3n+2)=8(3n+4)+6 | | f(x)=x^3-3x^2+2x-6 | | 5x^2+29xy-6y^2=0 | | 4(3c-1)-4=7c+2 | | 6(2n+2)=6(4n+1)+5 | | -0+9= | | 0.07x+0.11y=2.3 | | 5(3n+3)=7(8n+4)+2 |