If it's not what You are looking for type in the equation solver your own equation and let us solve it.
x in (-oo:+oo)
3-(x*((x-1)/2)) = 5 // - 5
3-(x*((x-1)/2))-5 = 0
(-1*x*(x-1))/2-5+3 = 0
(-1*x*(x-1))/2+(-5*2)/2+(2*3)/2 = 0
2*3-1*x*(x-1)-5*2 = 0
x-x^2-10+6 = 0
x-x^2-4 = 0
x-x^2-4 = 0
x-x^2-4 = 0
DELTA = 1^2-(-4*(-1)*4)
DELTA = -15
DELTA < 0
1 = 0
1/2 = 0
1/2 = 0 // * 2
1 = 0
x belongs to the empty set
| 120-15th=0 | | X/0.25=8 | | 8/7x=1 | | 120-15th=9 | | X+18.77=50 | | 5-7=3 | | 5/6x=1 | | 120-19=0 | | 1/9=a/(a+24) | | 3/8=x-5/16 | | 5x(7-2x)(9x+5)=0 | | -x(4x+7)=0 | | 3.4y=38.25 | | 2x^2+17x+30=9 | | 100y=3123 | | 2(x+6)=4x+18 | | X^2=-54 | | (1/2)10t^2+20t=385 | | 3x+3(x-65)=2445 | | 3x^2-10x-19=-11 | | 2a+3b=-8 | | 3x+9=10x-3 | | 24/x=48/60 | | 0.9x-3.6=3forx | | 4x-57=x | | n^3+5n^2-9n-45=0 | | 23/8=-1/2x | | 3(-2)-4=-10 | | X/3+2=2x/5 | | -6-4=-10 | | -8x=36 | | 6x^2+2x-10=13x |