a) = 76/35 ; 37/9
b) 143/40 ; 19/15
c) 2/3 ; 42/5
d) 21/4 ; 4/7
a, 11/7 + 3/5
= \(\dfrac{11x5}{7x5}+\dfrac{3x7}{5x7}=\dfrac{55}{35}+\dfrac{21}{35}=\dfrac{76}{35}\)
4 + 1/9
= \(\dfrac{4}{1}+\dfrac{1}{9}=\dfrac{4x9}{1x9}+\dfrac{1x1}{9x1}=\dfrac{36}{9}+\dfrac{1}{9}=\dfrac{37}{9}\)
b, 21/5 - 5/8
= \(\dfrac{21x8}{5x8}-\dfrac{5x5}{8x5}=\dfrac{168}{40}-\dfrac{25}{40}=\dfrac{143}{40}\)
2 - 11/15
=\(\dfrac{2}{1}-\dfrac{11}{15}=\dfrac{30}{15}-\dfrac{11}{15}=\dfrac{19}{15}\)
MIK LÀM ĐC NGẦN ĐẤY THUI BẸN THÔNG CẢM
c, \(\dfrac{3}{19}x\dfrac{38}{9}=\dfrac{114}{171}\)
\(\dfrac{21}{5}x2=\dfrac{21}{5}x\dfrac{2}{1}=\dfrac{42}{5}\)
d, \(\dfrac{7}{3}:\dfrac{4}{9}=\dfrac{7}{3}x\dfrac{9}{4}=\dfrac{63}{12}\)
\(\dfrac{12}{7}:3=\dfrac{12}{7}x\dfrac{1}{3}=\dfrac{12}{21}=\dfrac{4}{7}\)
câu 2 c bạn tự rút nha
a) = 76/35 ; 37/9
b) 143/40 ; 19/15
c) 2/3 ; 42/5
d) 21/4 ; 4/7
