bài 1:
a. 1,3 + 2,5 – 4,7 + 5,6 – 4,3=0,4
b.- 5,7 + 4,2 – 8,2 + 11,7=2
c. 25.(- 0,8).4.(-0,5).0,224=8,96
bài 2:
a.
\(x-\left|-7,5\right|=1,92+2,06\)
\(\Leftrightarrow x-7,5=3,98\)
\(\Rightarrow x=11,48\)
b.
\(5x-\left(-3,7\right)=-\left|-8,6\right|+5,75\)
\(\Leftrightarrow5x-3,7=-2,85\)
\(\Rightarrow x=-\dfrac{2,85+3,7}{5}=-1,31\)
c.
\(7,2+2x=-8,8-3,92\)
\(\Leftrightarrow7,2+2x=-12,72\)
\(\Rightarrow x=\dfrac{-12,72-7,2}{2}=-9,96\)
d.
\(10,8-x=0,24+3,76\)
\(\Leftrightarrow10,8-x=4\)
\(\Rightarrow x=6,8\)
bài 3:
a.
\(-13,45-7,98-8,55=-\left(13,45+7,98+8,55\right)=-29,98\)
b.
\(9,72+8,38+3,62=18,1+3,62=21,72\)
c.
\(\left|45,37\right|-\left|-29,73\right|+\left(-12,27\right)\)
\(=45,37-29,73-12,27\)
\(=\dfrac{4537}{100}-\dfrac{2973}{100}-\dfrac{1227}{100}=3,37\)
d.
\(31,71-7,41.15-2,59.15\)
\(=31,71-[15\left(7,41+2,59\right)]=-118,29\)