If it's not what You are looking for type in the equation solver your own equation and let us solve it.
D( k )
k = 0
k = 0
k = 0
k in (-oo:0) U (0:+oo)
(5*k)/7 = 40/k-15 // - 40/k-15
(5*k)/7-(40/k)+15 = 0
(5*k)/7-40*k^-1+15 = 0
5/7*k^1-40*k^-1+15*k^0 = 0
(5/7*k^2+15*k^1-40*k^0)/(k^1) = 0 // * k^2
k^1*(5/7*k^2+15*k^1-40*k^0) = 0
k^1
(5/7)*k^2+15*k-40 = 0
(5/7)*k^2+15*k-40 = 0
DELTA = 15^2-(-40*4*(5/7))
DELTA = 2375/7
DELTA > 0
k = ((2375/7)^(1/2)-15)/(2*(5/7)) or k = (-(2375/7)^(1/2)-15)/(2*(5/7))
k = 7/10*((2375/7)^(1/2)-15) or k = -7/10*((2375/7)^(1/2)+15)
k in { -7/10*((2375/7)^(1/2)+15), 7/10*((2375/7)^(1/2)-15)}
k in { -7/10*((2375/7)^(1/2)+15), 7/10*((2375/7)^(1/2)-15) }
| 2x(3)+2x(2)-60x=2x(x+6)(x-5) | | 68=a+7+2a+a+b | | 136=2x | | Log^2(4x-8)=5 | | -4(6r+5)-6r=220 | | x(2)+2x-8= | | 68=a+7+2a+b | | -4f^2+80f-188=0 | | s+443.62=-8.8s+3.6 | | x(2)+-3x-8= | | 210=5(7v+7) | | 68=a+7+a+b | | 4x=0.0256 | | p^2+2p-31=0 | | 0/15=3x | | -a+4=a+69.4 | | 4k(4)+32k(3)+60k(2)=4k(2)(k+3)(k+5) | | 82=-8-5(-2x-8) | | 3x^4-16x^2=0 | | 4v^2+104v-12=0 | | 2n+2.25=10.75 | | 4k(4)+32k(3)+60k(2)=-4k(2)(k-3)(k-5) | | 12x-15=9x-6 | | 83=-7+6(n+8) | | 3n-7=0 | | K^2+20k-13=0 | | 4-2y=-x | | n+55.5=-n+4.1 | | 2m^6-58m^4+200m^2=0 | | y-57=-52 | | 2h^2-52h+50=0 | | -4x^2+10x+1=10 |