Question

tìm x e Z bt :

a) x chia hét cho 12 ; x chia hết 25 ; x chia hết 30 và -300 < x < 600

b) x + ( x + 1) + ( x + 2) + ... + 2002 = 2002

c) (\(\frac{X}{10}\)- \(\frac{2}{3}\))²  -\(\frac{1}{25}\)= 0

Answer 1

\(\left(\frac{x}{10}-\frac{2}{3}\right)^2-\frac{1}{25}=0\)

\(\Leftrightarrow\left(\frac{x}{10}-\frac{2}{3}\right)^2=\frac{1}{25}\)

\(\Leftrightarrow\left(\frac{x}{10}-\frac{2}{3}\right)^2=\left(\pm\frac{1}{5}\right)^2\)

\(\Leftrightarrow\orbr{\begin{cases}\frac{x}{10}-\frac{2}{3}=\frac{1}{5}\\\frac{x}{10}-\frac{2}{3}=-\frac{1}{5}\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}x=\frac{26}{3}\\x=\frac{14}{3}\end{cases}}\)