x(x-1)/2=21这个方程怎么解

x(x-1)/2=21这个方程怎么解
x(x-1)/2=21这个方程怎么解

x(x-1)/2=21这个方程怎么解
x(x-1)/2=21
x(x-1)=42
x²-x-42=0
(x-7)(x+6)=0
x=7或x=-6

x²-x=42
x²-x-42=0
(x-7)(x+6)=0
x1=7,x2=-6

x(x-1)/2=21
x(x-1)=42
x^2 - x -42=0
因式分解
(x-7)(x+6)=0
x=7或-6

x(x-1)/2=21
x^2-x=42
x^2-x-42=0
(x-7)(x+6)=0
x=7或x=-6

x(x-1)/2=21
x(x-1)-42=0
x^2-x-42=0
(x-7)(x+6)=0
x1=7,x2=-6

X平方-X-42=0
X=-6 或者X=7