x2 - x - 2018.2919 = 0
<=> x2 - x - 5890542 = 0
(a = 1; b = -1; c = -5890542)
=> Δ = b2 - 4ac = (-1)2 - 4(-5890542) = 23562169
=> √∆ ~ 4854,08787
=> x1 = (-b - √∆) / 2a = (1 - 4854,08787) / 2 ~ -2426,54393
x2 = (-b + √∆) / 2a = (1 + 4854,08787) / 2 ~ 2427,54393
Vậy phương trình có 2 nghiệm: xx1 ~ -2426,54393 và x2 ~ 2427,54393
\(x^2-x-2018\cdot2019=0\)
\(\Leftrightarrow x^2-2019x+2018x-2018\cdot2019=0\)
\(\Leftrightarrow x\left(x-2019\right)+2018\left(x-2019\right)=0\)
\(\Leftrightarrow\left(x+2018\right)\left(x-2019\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x+2018=0\\x-2019=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-2018\\x=2019\end{matrix}\right.\)
Vậy...........