35.72 + 36.28

= 35. ( 72+28)

= 35 . 100 = 2500 

l-ike 

41 . 35 + 41 . 91 + 59 . 43 + 59 . 77 =  41( 35 + 91 ) + 59( 43 + 77 )

                                                      = 41 . 126 + 59 . 120 

................................................

 41.35+41.91+59.43+59.77

= 41.(35+91) + 59.(43+77)

= 41.126 + 59.120

= 5166 + 7080

= 12246

   41 x 35 + 41 x 91 + 59 x 43 + 59 x 77

= 41 x ( 35 + 91 ) + 59 x ( 43 + 77 )

= 41 x 126       + 59 x  120

= 5166            + 7080

= 12246

\(A=\frac{1}{3.41}+\frac{1}{4.42}+...+\frac{1}{33.71}\)

\(\Leftrightarrow A=\frac{1}{38}\left(\frac{1}{3}-\frac{1}{41}+\frac{1}{4}-\frac{1}{42}+...+\frac{1}{33}-\frac{1}{71}\right)\)

\(B=\frac{1}{3.34}+\frac{1}{4.35}+...+\frac{1}{46.71}\)

\(\Leftrightarrow B=\frac{1}{31}\left(\frac{1}{3}-\frac{1}{34}+\frac{1}{4}-\frac{1}{35}+...+\frac{1}{46}-\frac{1}{71}\right)\)

​\(\Leftrightarrow B=\frac{1}{31}\left(\frac{1}{3}-\frac{1}{41}+\frac{1}{4}-\frac{1}{42}+...+\frac{1}{33}-\frac{1}{71}\right)\)​

\(\Leftrightarrow\frac{A}{B}=\frac{31}{38}\)

(101 - 1) :2 + 1= 51

(101+1) x51:2=2601

\(-\left(25,1.3+23,1\right)+3.25,1-\left(1-28,1\right)\)

\(=-\left(3.25,1\right)-23,1+3.25,1-\left(-27,1\right)\)

\(=\left(-3.25,1+3.25,1\right)-23,1+27,1\)

\(=0+4=4\)               P/s : Giải khá dễ

a) Vì \(\widehat {t'AM} = \widehat {ABN}( = 65^\circ )\), mà 2 góc này ở vị trí đồng vị nên xx’//yy’ ( Dấu hiệu nhận biết 2 đường thẳng song song.)

b) Vì xx’//yy’ nên \(\widehat {x'MN} = \widehat {MNB}\)( 2 góc so le trong), mà \(\widehat {x'MN} = 70^\circ  \Rightarrow \widehat {MNB} = 70^\circ \)

A = 1/15 + 1/35 + 1/63 + 1/99 +........1/9999

A = 1/3x5 + 1/5x7 + 1/7x9 + .......+ 1/99x101

A = 1/2 x (1/3 - 1/5 + 1/5 - 1/7 + 1/7 - 1/9 +..... + 1/99 - 1/101)

A = 1/2 X ( 1/3 - 1/99)

A = 1/2 x ( 1/3 - 1/101)

A = 1/2 ( 98/303)

A = 49/303

49 / 303

tick cho mk nha

49/303

tick dum di

\(A=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{132}\)

\(=\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+...+\frac{1}{11\cdot12}\)

\(=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{11}-\frac{1}{12}\)

\(=1-\frac{1}{12}=\frac{11}{12}\)

Vậy \(A=\frac{11}{12}\)

Chúc bạn học tốt ^^!!!

\(A=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+...+\frac{1}{132}\)

\(=\frac{1}{1\times2}+\frac{1}{2\times3}+\frac{1}{3\times4}+...+\frac{1}{11\times12}\)

\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{11}-\frac{1}{12}\)

\(=1-\frac{1}{12}=\frac{11}{12}\)

Chúc bạn học tốt!

#Huyền#

 A=\(\frac{1}{2}\)+\(\frac{1}{6}\)+\(\frac{1}{12}\)+.....+\(\frac{1}{132}\)

A= \(\frac{1}{1x2}\)+\(\frac{1}{2x3}\)+\(\frac{1}{3x4}\)+.....+\(\frac{1}{11x12}\)

A= 1  -\(\frac{1}{2}\)+ \(\frac{1}{2}\)-\(\frac{1}{3}\)+\(\frac{1}{3}\)-\(\frac{1}{4}\)+....+\(\frac{1}{11}\)-\(\frac{1}{12}\)

A= 1-\(\frac{1}{12}\)

A=\(\frac{11}{12}\)