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^2-(4*x)-21 = 0
x^2-(4*x)-21 = 0
x^2-(4*x)-21 = 0
x^2-4*x-21 = 0
x^2-4*x-21 = 0
DELTA = (-4)^2-(-21*1*4)
DELTA = 100
DELTA > 0
x = (100^(1/2)+4)/(1*2) or x = (4-100^(1/2))/(1*2)
x = 7 or x = -3
x in (-oo:-3) U (-3:7) U (7:+oo)
(x^2+4*x+21)/(x^2-(4*x)-21)-((9*x+35)/(x^2-(4*x)-21)) = 0
(x^2+4*x+21)/(x^2-4*x-21)-((9*x+35)/(x^2-4*x-21)) = 0
(x^2+4*x+21)/(x^2-4*x-21)+(-1*(9*x+35))/(x^2-4*x-21) = 0
x^2-4*x-21 = 0
x^2-4*x-21 = 0
x^2-4*x-21 = 0
DELTA = (-4)^2-(-21*1*4)
DELTA = 100
DELTA > 0
x = (100^(1/2)+4)/(1*2) or x = (4-100^(1/2))/(1*2)
x = 7 or x = -3
(x+3)*(x-7) = 0
(x^2+4*x+21)/((x+3)*(x-7))+(-1*(9*x+35))/((x+3)*(x-7)) = 0
x^2-1*(9*x+35)+4*x+21 = 0
x^2-5*x-14 = 0
x^2-5*x-14 = 0
x^2-5*x-14 = 0
DELTA = (-5)^2-(-14*1*4)
DELTA = 81
DELTA > 0
x = (81^(1/2)+5)/(1*2) or x = (5-81^(1/2))/(1*2)
x = 7 or x = -2
(x+2)*(x-7) = 0
((x+2)*(x-7))/((x+3)*(x-7)) = 0
((x+2)*(x-7))/((x+3)*(x-7)) = 0 // * (x+3)*(x-7)
(x+2)*(x-7) = 0
( x+2 )
x+2 = 0 // - 2
x = -2
( x-7 )
x-7 = 0 // + 7
x = 7
x in { 7}
x = -2
| (13t+7)(6t-18)=0 | | (6u+7)/5=(u-3)/6+(5) | | 6u+7/5=u-3/6+5 | | 32x+24=5(2x-4) | | (w-1/w+2)+1=(w-7/w-6) | | (3x+2)/10-6=0 | | 3x-7=6x+20 | | 3(x-5)=7+x | | 8x-14/3x | | -2(x-5)=-16 | | 5x+3x+6x= | | 7x=-55 | | .15(x)+.08(y)=1.92 | | 12r^5(r^3)^3/11(r^-2)^2 | | x-4x+6=12 | | -5.8+2.6= | | 17-(4-62)+4=42 | | 3x-2(4x+3)=3x-5 | | 3s+4d= | | 2(2y-7)-8(y+6)=31 | | ((3x+7)/10)-6=0 | | 8x-9-7x+8=3x+5 | | 2k+3=4 | | 7x-8+3x+5=8x-9 | | k(2+3)=4 | | (3x+7)/10-6=0 | | w^2-9/4=0 | | kx+y=4 | | 3z^2+4z-4=0 | | 64+225=c^2 | | (m^2-3)x^2+3mx+3m+1=0 | | 4(x-8)-6x=3x-x-8 |