Bài 1:
a) \(\dfrac{7}{23}+\dfrac{4}{17}-\dfrac{7}{23}+\dfrac{13}{17}\)
= \(\left(\dfrac{7}{23}-\dfrac{7}{23}\right)+\left(\dfrac{4}{17}+\dfrac{13}{17}\right)\)
= \(\dfrac{0}{23}+\dfrac{17}{17}\)
= \(0+1\)
= 1
chúc bạn học tốt nhé !
Bài 1 :
b) \(19\dfrac{1}{4}.\dfrac{7}{12}-15\dfrac{1}{4}.\dfrac{7}{12}\)
= \(\dfrac{7}{12}.\left(19\dfrac{1}{4}-15\dfrac{1}{4}\right)\)
= \(\dfrac{7}{12}.4\)
= \(\dfrac{7}{3}.1\)
= \(\dfrac{7}{3}\)
Mk gửi nốt câu b nha !
Bài 3:
a) Để phân số \(\dfrac{7}{n-2}\) là số nguyên thì \(7⋮n-2\)
\(\Leftrightarrow n-2\in\left\{1;-1;7;-7\right\}\)
hay \(n\in\left\{3;1;9;-5\right\}\)