How to solve the equation x (x-1) / 2 = 21

How to solve the equation x (x-1) / 2 = 21


x(x-1)/2=21
x(x-1)=42
x²-x-42=0
(x-7)(x+6)=0
X = 7 or x = - 6



How to do the equation 3x + 2 (9-x) = 21?


3x+2(9-x)=21
3x+18-2x=21
(3-2)x=21-18
x=3



To solve the linear equation of one variable: X-1 of X-5 = x + 1 of 2-2


x-x/5+x/2=1+1
13x/10=2
x=20/13 .
10x-2(x-1)=20-5(x+1)
10x-2x+2=20-5x-5
10x-2x+5x=20-5-2
13x=13
x=1.



To solve the linear equation of one variable, 4 / x + 2 / x + x = 21


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