\(\text{a)4,38-19+0,62}\)\(=-14\)

\(b.3,45-5,7+8,55=6,3\)

\(c.14,7+\left(-8,4\right)+\left(-4,7\right)=1.6\)

2.

\(a,-2,4-\left(0,54-2,5\right)=-0,44\)

\(b,-25,4-\left(5,54-2,5\right)=-28,44\)

\(c.2,15-\left(-0,6+0,12\right)=2.63\)

CẢM ƠN BẠN NHIỀU=)

a) 14,7 + (-8,4) + (-4,7) = (14,7 - 4,7) + (-8,4)

= 10 - 8,4 = 1,6

b) (-4,2).5,1 + 5,1.(-5,8) = 5,1. (- 4,2 - 5,8)

= 5,1. (-10) = -51

c) (-0,4: 0,04 + 10) . (1,2.20 + 12.8)

= (-10 + 10). (1,2.20 + 12.8)

= 0. (1,2.20 + 12.8) = 0.

\(\frac{-9}{2}+\left[\left(-5,8\right)-\left(-4,7\right)\right]\)

\(=\left(-4,5\right)+\left(-5,8\right)+4,7\)

\(=\left(-10,3\right)+4,7\)

\(=5,6\)

Đ/S:7140

tích mình nhé

1. \(\dfrac{2}{3}\)*\(\dfrac{x}{4}\)=\(\dfrac{5}{6}\)-\(\dfrac{2}{3}\)

\(\dfrac{2x}{12}\)=\(\dfrac{5}{6}\)-\(\dfrac{4}{6}\)

\(\dfrac{x}{6}\)=\(\dfrac{1}{6}\)

x=1

2.a, hai số x sao cho 3,9<x<4,1 là 3,91 và 4 (tùy bạn chon nha)

b, 14,7+0,35*3,78-10,8

=14,7 +1,323-10,8

=16,023-10,8

= 5,223

mãi mới trả lời,mình nộp bài đấy cho cô mấy ngày trước rồi.

Dấu " . " k p dấu " , "

a) \(\frac{91}{1\cdot4}+\frac{91}{4\cdot7}+\frac{91}{7\cdot10}+...+\frac{91}{88\cdot99}\)

* Bài đúng k z ???

b) \(5\frac{1}{7}\left(3\frac{2}{3}+4\frac{1}{7}\right)=\frac{36}{7}\cdot\left(\frac{11}{3}+\frac{29}{7}\right)\)

\(=\frac{36}{7}\cdot\frac{164}{21}=\frac{1968}{49}\)

a/ Ta có: \(S=1+\left(\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+....+\frac{1}{27}-\frac{1}{30}\right)\)

\(S=1+\left(\frac{1}{2}-\frac{1}{30}\right)\)

\(S=1+\frac{7}{15}\)

\(S=\frac{22}{15}\)

b/ \(S=-4+\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+...+\frac{1}{107}-\frac{1}{110}\right)\)

\(S=-4+\left(1-\frac{1}{110}\right)\)

\(S=-4+\frac{109}{110}\)

\(S=-3\frac{1}{110}\)