1)   29,37- (5,25+4,12)=29,37-9,37=20

2)   26(13+173-86)=26. 100=2600

\(=-23.6\left(14.1+5.9\right)-6.4\cdot12.4+32.4\cdot6.4\)

\(=-23.6\cdot20+6.4\cdot20\)

\(=20\cdot\left(-17.2\right)=-344\)

cảm ơn ạ

a: (-4,2)+(-15,6)+35+(-5,8)+(-4,4)

=(-4,2-5,8)+(-15,6-4,4)+35

=-10-20+35

=35-30=5

b: \(11,2\cdot\left(-3,5\right)+8,8\cdot\left(-3,5\right)\)

\(=-3,5\cdot\left(11,2+8,8\right)\)

\(=-3,5\cdot20=-70\)

c: \(14,1\cdot\left(-23,6\right)-6,4\cdot12,4+5,9\cdot\left(-23,6\right)-32,4\cdot\left(-6,4\right)\)

\(=\left(-23,6\right)\left(14,1+5,9\right)+6,4\left(32,4-12,4\right)\)

\(=-23,6\cdot20+6,4\cdot20=20\cdot\left(-23,6+6,4\right)=20\cdot\left(-17.2\right)=-344\)

d: \(\left(-53,4\right)-68,3-11,7-20,1+\left(-26,6\right)\)

=(-53,4-26,6)+(-68,3-11,7)-20,1

=-80-80-20,1

=-180,1

a) 32,4 x 6,34 + 3,66 x 32,4 +5= 32,4 x ( 6,34 + 3, 66)+5 

= 32,4 x 10 + 5

= 324 + 5

329

Phần b tương tự

bt thôi

A= \(\dfrac{2}{1.4}+\dfrac{2}{4.7}+...+\dfrac{2}{16.19}\) 

A= \(\dfrac{2}{3}.\left(\dfrac{3}{1.4}+\dfrac{3}{4.7}+...+\dfrac{3}{16.19}\right)\)

A= \(\dfrac{2}{3}.\left(\dfrac{1}{1}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+...+\dfrac{1}{16}-\dfrac{1}{19}\right)\) 

A= \(\dfrac{2}{3}.\left(\dfrac{1}{1}-\dfrac{1}{19}\right)\) 

A= \(\dfrac{2}{3}\) . \(\dfrac{18}{19}\) 

A= \(\dfrac{36}{57}\)

1/1.4+1/4.7+1/7.10+...+1/16.19

=[1/1.4+1/4.7+1/7.10+...+1/16.19] x 3

= 3/1.4+3/4.7+3/7.10+...+3/16.19

= 1-1/4+1/4-1/7+1/7-1/10+....+1/16-1/19

=1-1/19

=18/19 :3

=6/19

ĐÂY BẠN NHÉ CHÚC BẠN HỌC TỐT NHỚ K CHO MÌNH

A = \(\dfrac{1}{10}+\dfrac{1}{15}+...+\dfrac{1}{120}\)

A= \(\dfrac{2}{2}.\left(\dfrac{1}{10}+\dfrac{1}{15}+...+\dfrac{1}{120}\right)\) 

A= \(2.\left(\dfrac{1}{20}+\dfrac{1}{30}+...+\dfrac{1}{240}\right)\)

A= \(2.\left(\dfrac{1}{4.5}+\dfrac{1}{5.6}+...+\dfrac{1}{15.16}\right)\) 

A=\(2.\left(\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+...+\dfrac{1}{15}-\dfrac{1}{16}\right)\)

A=\(2.\left(\dfrac{1}{4}-\dfrac{1}{16}\right)\) 

A=\(\dfrac{2.3}{16}\) 

A= \(\dfrac{3}{8}\)