= 63. \([\) (-121) + ( -53 ) - 26 \(]\)

= 63. ( -200 )

= -12600

ta có: 2005 + 53-54-55+56-57-58-59+60+61-62-63+64+65-66-67+68+69

      = 2005+(53-54-55+56)+(57-58-59+60)+(61-62-63+64)+(65-66-67+68)+69

      = 2005+0+0+0+0+69

      = 2005+69

      = 2074

37 . 75 + 37 . 45 + 63 . 67 + 63 . 53 

= ( 75 + 45 ) . 37 + ( 67 + 53 ) . 63

=      120 . 37 +           120 . 63 

=       120 . ( 37 + 63 )

=       120 . 100

=        12000

37.75+37.45+63.67+63.53

=37(75+45)+63(67+53)

=37.120+63.120

=(37+63)120

=100.120

=12000

tk nha phamthiminhtrang

a. -15 . 999 
=-14985
b. 121. (-63) +63 .(-53) -63.26
=-7623+(-3339)-1638
=-10962-1638
=-12600
c. [299. (-74) + (-299) . (-24)] : (-50).
=[-22126+7176]:(-50)
=-14950:(-50)
=299
d. [900 + (-1140) + 720 ] : (-120)
=[-240+720]:(-120)
=480:(-120)
=-4
e. 6. (-4 2 ). (-102 ) : 24 
=-252.(-102):24
=25704:24
=1071
f. [(-8).(-8).(-8).(-8) + 84 ] : 8100
=[64.(-8).(-8)+84]:8100
=[-512.(-8)+84]:8100
=[4096+84]:8100
=4180:8100
=0,51

=\(\frac{1}{3\cdot5}+\frac{1}{5.7}+\frac{1}{7.9}+...+\frac{1}{11\cdot13}=\frac{1}{2}\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{11}-\frac{1}{13}\right)\)

\(=\frac{1}{2}\left(\frac{1}{3}-\frac{1}{13}\right)=\frac{1}{2}.\frac{10}{13}=\frac{5}{13}\) 

B=1/15+1/35+1/63+1/99+1/143

B=1/3.5+1/5.7+1/7.9+1/9.11+11.13    (khoảng cách từ 3-5;5-7;7-9;9-11;11-13 la 2)

Suy ra B=1/2(1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13) (Ta gop -1/5+1/5;-1/7+1/7;-1/9+1/9;-1/11+1/11 bang 0)

B=1/2(1/3-1/43)=1/2.40/129=20/129

\(\dfrac{63^3-37^3}{26}+\dfrac{63}{37}\)

\(=100+2\cdot63\cdot37+\dfrac{63}{37}\)

\(=\dfrac{176257}{37}\)

\(\dfrac{63^3-37^3}{26}+\dfrac{63}{37}\)

\(=100+2\cdot63\cdot37+\dfrac{63}{37}\)

\(=\dfrac{176257}{37}\)

63 x 178 - 53 x 178

=178 x ( 63 - 53 )

=178 x 10

=1780

63 x178 - 53 x 178 = (63-53)x178 = 10 x178 = 1780 nha e , 100% đúng nha

`1/15+1/35+1/63+1/99+1/143`

`=1/[3.5]+1/[5.7]+1/[7.9]+1/[9.11]+1/[11.13]`

`=1/2(2/[3.5]+2/[5.7]+2/[7.9]+2/[9.11]+2/[11.13])`

`=1/2.(1/3-1/5+1/5-1/7+...+1/11-1/13)`

`=1/2.(1/3-1/13)`

`=1/2 . 10/39`

`=5/39`

Đáp án cần chọn là: B

Ta có: 57+26+34+63=(57+63)+(26+34)=120+60=180