Question

[Sách Giáo Khoa]

Điền các số thích hợp vào bảng sau : 

a	\(\dfrac{-3}{4}\)	\(\dfrac{5}{9}\)	\(\dfrac{-7}{25}\)		\(\dfrac{4}{7}\)	\(\dfrac{-4}{19}\)	\(\dfrac{-18}{15}\)		\(\dfrac{50}{21}\)
b	\(\dfrac{4}{7}\)	\(\dfrac{-18}{15}\)	\(\dfrac{50}{21}\)	\(\dfrac{-3}{7}\)	\(\dfrac{-3}{4}\)		\(\dfrac{5}{9}\)	\(\dfrac{6}{13}\)	\(\dfrac{-7}{25}\)
a.b				\(1\)		\(\dfrac{-4}{19}\)		\(0\)

Answer 1

[Nguyễn Lê Phước Thịnh]

a=-3/4; b=4/7 =>ab=-3/7

\(a=\dfrac{5}{9};b=-\dfrac{18}{15}=-\dfrac{6}{5}\Leftrightarrow ab=-\dfrac{2}{3}\)

\(a=-\dfrac{7}{25};b=\dfrac{50}{21}\Leftrightarrow ab=-\dfrac{2}{3}\)

\(ab=1;b=-\dfrac{3}{7}\Leftrightarrow a=-\dfrac{7}{3}\)

\(a=\dfrac{4}{7};b=-\dfrac{3}{4}\Leftrightarrow ab=-\dfrac{3}{7}\)

\(a=\dfrac{-4}{19};ab=-\dfrac{4}{19}\Leftrightarrow b=1\)

\(a=-\dfrac{18}{15}=-\dfrac{6}{5};c=\dfrac{5}{9}\Leftrightarrow ab=-\dfrac{2}{3}\)

\(ab=0;b=\dfrac{6}{13}\Leftrightarrow a=0\)