bài 1:tính
a)\(\left(\dfrac{-7}{15}-\dfrac{27}{70}\right)-\left(\dfrac{8}{15}+\dfrac{43}{70}\right)\)
b)\(\dfrac{3}{7}+\left(\dfrac{-1}{5}+\dfrac{-3}{7}\right)\)
c)\(\left(4-\dfrac{12}{5}\right).\dfrac{25}{8}-\dfrac{2}{5}:\dfrac{-4}{25}\)
d)\(\left(\dfrac{-5}{24}+\dfrac{3}{4}-\dfrac{7}{12}\right):\left(-\dfrac{5}{16}\right)\)
e)\(\dfrac{-5}{7}.\dfrac{2}{11}+\dfrac{-5}{7}.\dfrac{9}{11}\)
g)\(\dfrac{6}{7}+\dfrac{5}{4}:\left(-5\right)-\dfrac{-1}{28}.\left(-2\right)^2\)
Giải:
a)(-7/15-27/70)-(8/15+43/70)
=-7/15-27/70-8/15-43/70
=(-7/15-8/15)+(-27/70-43/70)
=-1+(-1)
=-2
b)3/7+(-1/5+-3/7)
=3/7-1/5+-3/7
=(3/7+-3/7)-1/5
=0-1/5
=-1/5
c)(4-12/5).25/8-2/5:-4/25
=8/5.25/8-(-5/2)
=5+5/2
=15/2
d)(-5/24+3/4-7/12):(-5/16)
=-1/24:(-5/16)
=2/15
e)-5/7.2/11+-5/7.9/11
=-5/7.(2/11+9/11)
=-5/7.1
=-5/7
g)6/7+5/4:(-5)-(-1/28).(-2)2
=6/7+(-1/4)-(-1/28).4
=6/7+(-1/4)-(-1/7)
=6/7-1/4+1/7
=(6/7+1/7)-1/4
=1-1/4
=3/4
Chúc bạn học tốt!