a)

\( 49.(51 - 4) - 51.(49 + 4)\)

\(=49.51-49.4-51.49-51.4\)

\(=49.(51-4-51)-51.4\)

\(=49.(-4)-51.4\)

\(=4.(-49-51)\)

\(=4.(-100)\)

\(=-400\)

b)

\( 71.64 + 32.(-7) - 13.32\)

\(=71.32.2+32.(-7)-13.32\)

\(=142.32+32.(-7)-13.32\)

\(=32.(142-7-13)\)

\(=32.122\)

\(=3904\)

c)

\( 11 + (-13) + 15 + (-17) + ... + 59 + (-61)\)

\(=(-2)+(-2)+...+(-2)\)

\(=(-2).13\)

\(=-26\)

a. 49.51- 49.4 -51.49 -51.4

= -49.4 - 51.4

=4.(-49-51)

=4.-100

=-400

b.71.64 + 32.(-7) -13.32

= 71.64 + 32.(-7-13)

=71.64 + 32.-20 

=71.32.2 +32.-20

=32.(71x2-20)

=32. 122

= 3904

c. (11-13)+(15-17)+..+(59-61)

=-2 x 13

=-26

a,1-2+3-4+...+49-50.

=(-1)+(-1)+...+(-1)

=-25

b,1-4+7-10+...-100+103

=(-3)+(-3)+...+(-3)+103

=(-150)+103

=-47

a) 1 - 2 + 3 - 4 + ... + 49 - 50

= -1 + (-1) + ... + (-1)

= -1 . [(50 - 1) + 1] : 2

= -1 . 25

= -25

b) 1 - 4 + 7 - 10 + ... - 100 + 103

= -3 + (-3) + ... + (-3) + 103

= -3 . [(100 - 1) : 3 + 1] : 2 + 103

= -3 . 34 : 2 + 103

= -3 . 17 + 103

= -51 + 103

= 52

= -47

tk mk nha

bn sakuura sai

a)    \(\left(-25\right).5.\left(-4\right).2\)

\(=\left[\left(-25\right).\left(-4\right)\right].\left(2.5\right)\)

\(=100.10=1000\)

b)   \(\left(-456\right)-\left(67-456\right)\)

\(=-456-67+456\)

\(=\left(456-456\right)-67\)

\(=67\)

a) ((-25).(-4)).5.2

=100.10

=1000

b) (-456)-67+456

=(-456)+(-67)+456

=0+-(-67)

=-67

c)78.45+-145.78

=78.(45+145)

=78.190

=Tự làm

a) (-25).5.(-4).2

= 5 . ( -4 ) . ( -25 ) . 2

= -20 . ( - 50 )

= 100

b) (-456) - (67 - 456)

= -456 - 67 + 456

= -456 + 456 - 67

= -67

c) 78.45+145.(-78)

= 78 . 45 + ( - 145 ) . 78

= 78 . ( -145 + 45 )

= 78 . 100

= 7800

d) 38.( 62-75) + 62.(-75 - 38)

= 38 . 62 - 38 . 75 + 62 . ( - 75 ) - 62 . 38

= 38 . 62 - 62 . 38 + 38 . 75 + 62 . ( - 75 )

= 0 + 38 . 75 + ( - 62 ) . 75

= 75 . ( - 62 + 38 )

= 75 . ( - 24 )

= - 1800

a) 125.(-4).(-8).7

= 125 . ( - 8 ) . ( - 4 ) . 7

= 1000 . ( - 28 )

= - 28000

c) 72.( 28 - 49) + 28. ( -49 - 72)

= 72 . 28 - 72 . 49 + 28 . ( - 49 ) - 28 . 72

= 72 . 28 - 28 . 72 + 72 . 49 + 28 . ( - 49 )

= 0 + 72 . 49 + ( - 28 ) . 49

= 49 . ( -28 + 72 )

= 49 . 44

= 2156

\(=\dfrac{1-\dfrac{1}{7}+\dfrac{1}{49}-\dfrac{1}{343}}{\dfrac{8}{2}-\dfrac{4}{7}+\dfrac{4}{49}-\dfrac{4}{343}}=\dfrac{1-\dfrac{1}{7}+\dfrac{1}{49}-\dfrac{1}{343}}{4-\dfrac{4}{7}+\dfrac{4}{49}-\dfrac{4}{343}}=\dfrac{1}{4}\)

a) (-2) + 7 + (-12) + 17 + ... + (-52) + 57

= (-2 + 7) + (-12 + 17) + ... + (-52 + 57)

= 5 + 5 + ... + 5 (6 chữ số 5)

= 30

b) (-30) + (-29) + (-28) + ... + 49 + 50

= 31 + 32 + ... + 49 + 50

= (50 + 31) . (50 - 31 + 1) : 2

= 81 . 10

= 810

Tính hợp lí

a,15.(27+ 18 +6 ) + 15.( 23 +12)

  = 15(27+18+6+23+12)

  = 15.86

  = 1290

b,24.(15 + 49 ) + 12. ( 50 + 42 )

=12.2(15+49)+12.(50+42)

= 12(30+98)+12(50+42)

=12(30+98+50+42)

=12.220

= 2640

c,53.(51+4)+53.(49+96) +53

=53(51+4)+53(49+96)+53.1

=53(51+4+49+96+1)

=53.201

=10653

d,42.( 15 +96) +6.(25 +4).7  

=42(15+96)+42(25+4)

=42(15+96+25+4)

=42.140

=5880

tick đúng cho mk nha pikachu

20-2.(x+14)=16

Tính hợp lí:

\(a)\)\(15.\left(27+18+6\right)+15.\left(23+12\right)\)

\(=\)\(15.51+15.35\)

\(=\)\(15.\left(51+35\right)\)

\(=\)\(15.86\)

\(=\)\(1290\)

\(b)\)\(24.\left(15+49\right)+12.\left(50+42\right)\)

\(=\)\(24.64+12.92\)

\(=\)\(1536+1104\)

\(=\)\(2640\)

\(c)\)\(53.\left(51+4\right)+53.\left(49+96\right)+53\)

\(=\)\(53.55+53.145+53\)

\(=\)\(53.\left(145+55+1\right)\)

\(=\)\(53.201\)

\(=\)\(10653\)

\(d)\)\(42.\left(15+96\right)+6.\left(25+4\right).7\)

\(=\)\(42.\left(15+96\right)+42.\left(25+4\right)\)

\(=\)\(42.111+42.29\)

\(=\)\(42.140\)

\(=\)\(5880\)

a,(-2)+7+(-12)+17+...+(-52)+57

=[(-2)+7]+[(-12)+17]+...+[(-52)+57]

=5+5+5+...+5               có 6 số 5

=5.6

=30

b,(-30)+(-29)+...+48+49+50

=[(-30)+(-29)]+...+31+32+...+50

=0+0+...+31+32+...+50

=0+31+32+...+50

=810

a, (-2+7)+(-12+17)+...+(-52+57)

=5+5+...+5

=5.6=30

b,(-30)+(-29)+...48+49+50

=(-30+30)+(-29+29)+...+(-1+1)+0+31+32+...+50

=0+0+0+...+0+31+32+...+50

=20.(31+50)=20.81=1620