6.75*3=20.25

(7.14*3)*3=64.26

(9.26*2)*9=166.68

Bài làm

~ Mik nghĩ là đề bài là 7.12×9+7.12×2_7.12 thì hợp lí hơn, nhg mik làm cả hai.

Đề 1: 7.14 × 9 + 7.12 × 2 - 7.12 ( đề của bạn )

= 7,14 x 9 + 7,12 x ( 2 - 1 )

= 7,14 x 9 + 7,12 x 1

= 64,26 + 7,12

= 71,38

Đề 2: 7.12 × 9 + 7.12 × 2 - 7.12 ( đề của mik )

= 7,12 x ( 9 + 2 - 1 )

= 7,12 x 10

= 71,2

# Chúc bạn học tốt #

7,14x5=35,7

tk nha

7,14+7,14+7,14x3

=7,14x(1+1+3)

=7,14x5

=35,7

  7 x 14m² +7 x 14m² + 7 x 14m²

= (7+7+7) x ( 14m²+ 14m²+ 14m²)

=7 x 3 + 14m²x 3

=21 + 42m²

\(\frac{5}{7}.\frac{5}{11}+\frac{5}{7}.\frac{2}{11}-\frac{5}{7}.\frac{14}{11}\)

\(=\frac{5}{7}.\left(\frac{5}{11}+\frac{2}{11}-\frac{14}{11}\right)\)

\(=\frac{5}{7}.\frac{-7}{11}\)

\(=\frac{-5}{11}\)

5/7.5/11+5/7.2/11-5/7.14/11

= 5/7.(5/11+2/11-14/11)

=5/7.-7/11

=-5/11

5/7 + 5/11 + 5/7 . 2/11 - 5/7 .14/11

=5/7.(5/11+2/11-14/11)

=5/7.(5+2-4/11)

=5/7.(-7/11)

=-5/11

-41/28

\(\frac{2}{3}-\frac{5}{7}\cdot\frac{14}{225}\)

\(=\frac{2}{3}-\frac{2}{45}\)

\(=\frac{28}{45}\)

Tk mk nha!

 \(\frac{2}{3}-\frac{5}{7}\cdot\frac{14}{225}\)

\(=\frac{2}{3}-\frac{5\cdot14}{7\cdot225}\)

\(=\frac{2}{3}-\frac{5\cdot7\cdot2}{7\cdot5\cdot45}\)

\(=\frac{2}{3}-\frac{2}{45}\)

\(=\frac{30}{45}-\frac{2}{45}\)

\(=\frac{28}{45}\)

tk mình nha!   ◘_◘

2/3-5/7.14/225=2/3-2/45=28/45

NHA 

sorry

ai gúp tớ với

\(4\&\frac{2}{5}.0,5-1\&\frac{3}{7}.14\%+\left(-0,8\right)\)

\(\frac{2}{5}.0,5-1=\frac{2}{5}.\frac{5}{10}-1=\frac{1}{5}-\frac{5}{5}=\frac{-4}{5}\)

\(\frac{3}{7}.14\%+\left(-0.8\right)=\frac{3}{7}.\frac{7}{50}-\frac{4}{5}=\frac{3}{50}-\frac{40}{50}=\frac{-37}{50}\)

\(VI\frac{-4}{5}=\frac{-40}{50}< \frac{-37}{50}MA\frac{-37}{50}< 0< 4\Rightarrow\frac{-4}{5}< \frac{-37}{50}< 4\)⁽¹⁾

^{TỪ 1 =>\(\frac{2}{5}.0,5-1< \frac{3}{7}.14\%+\left(-0,8\right)< 4\)}

A =\(\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{14}+\frac{1}{14}-\frac{1}{21}+...+\frac{1}{140}-\frac{1}{150}\)

A=\(\left(\frac{1}{3}-\frac{1}{150}\right)\)

A=\(\left(\frac{50}{150}-\frac{1}{150}\right)\)

A=\(\frac{49}{150}\)

\(A=\frac{1}{3x7}+\frac{1}{7x14}+....+\frac{1}{140x150}\)

\(A=\frac{1}{3}-\frac{1}{7}+.....+\frac{1}{140}-\frac{1}{150}\)

\(A=\frac{1}{3}-\frac{1}{150}\)

\(A=\frac{49}{150}\)

\(A=\frac{1}{3x7}+\frac{1}{7x14}+....+\frac{1}{140x150}\)

\(A=\frac{1}{3}-\frac{1}{7}+.....+\frac{1}{140}-\frac{1}{150}\)

\(A=\frac{1}{3}-\frac{1}{150}\)

\(A=\frac{49}{150}\)