${(x-4).(8-x) =0}$
⇒ \(\left[ \begin{array}{l}x-4=0\\8-x=0\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x=0+4\\x=8-0\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x=4\\x=8\end{array} \right.\)
$\text{Vậy \(\left[ \begin{array}{l}x=4\\x=8\end{array} \right.\)}$
${5.7.77-7.50+49.25-15.42}$
= ${5.7.7.11- 7.5.12+ 7.7.5.5- 5.3.7.6}$
= ${5.7.11-5.7.12+5.7.35-5.7.18}$
= ${5.7( 77- 12+ 35 - 18)}$
= ${35.82}$
= ${2870}$
$\text{CHÚC EM HỌC TỐT!}$
