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Bài 1:
a: \(\dfrac{a}{b}=\dfrac{a\cdot\left(-1\right)}{b\cdot\left(-1\right)}=\dfrac{-a}{-b}\)
b: \(\dfrac{a}{-b}=-\dfrac{a}{b}=-\dfrac{a}{b}\)
a) \(\left(a-b-d\right)+\left(b-a-d\right)=a-b-d+b-a-d\)
\(=\left(a-a\right)-\left(b-b\right)-\left(d+d\right)\)
\(=0-2d\)
\(=-2d\)
b) \(-\left(a-b+c\right)-\left(a-b-c\right)=-a+b-c-a+b+c\)
\(=\left(-a-a\right)+\left(b+b\right)-\left(c-c\right)\)
\(=-2a+2b\)
c) \(\left(c-a+d\right)+\left(a-b-d\right)=c-a+d+a-b-d\)
\(=c-\left(a-a\right)+\left(d-d\right)-b\)
\(=c-b\)
a ) \(\left(a-b-d\right)+\left(b-a-d\right)=a-b-d+b-a-d=-2d\)
b ) \(-\left(a-b+c\right)-\left(a-b-c\right)=-a+b-c-a+b+c=-2a+2b=2\left(-a+b\right)\)
c ) \(\left(c-a+d\right)+\left(a-b-d\right)=c-a+d+a-b-d=c-b\)
a)A=1+22+24+...+214+216
2A=2(1+22+24+...+214+216)
2A=2+23+25+...+215+217
2A-A=(2+23+25+...+215+217)-(1+22+24+...+214+216)
1A=(217-1)/1
A=217-1
b)B=1-3+32-33+...-32015+32017
3B=3(1-3+32-33+...-32015+32017)
3B=3-32+33-...-32016+32017)
Mà B=1-3+32-33+...-32015+32017
=>3B-B=1+22017
=>4B=1+32016
=>B=(1+32017)/4
a)\(\left(a+b\right)\left(a-b\right)-a^2+b^2\)
\(=a^2-b^2-a^2+b^2=0\)
b)\(\left(-a+b\right)\left(a-b\right)+a^2+b^2\)
\(=-a^2+2ab-b^2+a^2+b^2=2ab\)
c)\(a\left(b+c\right)-b\left(c-a\right)+c\left(b-a\right)\)
\(=ab+ac+ab-bc+bc-ac\)
\(=ab+ab=2ab\)
d)\(\left(a+b\right)\left(c+d\right)-\left(a-b\right)\left(c-d\right)\)
\(=ac+ad+bc+bd-ac+ad+bc-bd\)
\(=2ad+2bc=2\left(ad+bc\right)\)
a)2354-45-2345=2354-2354-45=-45. b)-2009-243+2009=-2009+2009-234+-243. c)16+23+153-16-23=16-16+23-23+153=153.d)134-167+45-134-45=134-134+45-45-167=-167.e)215+43-215-25=215-215+43-25=18.f)-312-327-28+27-312-28-327+27=340-300=40
a, (2354-45)-2354
=2354-45-2354
=(2354-2354)-45
=0-45
=-45
a/ 5 ^ 23 và 6. 5^ 22
5^23= 5.5^22
=> 5^23<6.5^22
b/ 7.2 ^ 13 và 2 ^ 16
2^16= 2^3.2^13= 8.2^13
=> 7.2^13<2^16
c/21^ 15 và 27^ 5 . 49 ^ 8
21^ 15=(7.3)^15=3^15.7^15
27^ 5 . 49 ^ 8=27^5.(7^2)^8=27^5.7^16
27^ 5 = 3^5.9^5=3^5.(3^2)^5=3^5.3^10=3^15
vì 3^15.7^15<3^15.7^16
nên 21^15< 27^ 5 . 49 ^ 8
ok men
a, (2354 - 45) - 2354
= 2354 - 45 - 2354 = ( 2354 - 2354 ) - 45 = 0 - 45 = -45
b, (-2009 ) - ( 234 - 2009 )
= (-2009 ) - 234 + 2009 = ( -2009 + 2009 ) -234 = 0- 234 = -234
c, ( 16 + 23 ) + ( 153 - 16 - 23 )
= 16 + 23 + 153 - 16 - 23 = ( 16 - 16 ) + ( 23 - 23 ) + 153 = 0 + ) + 153 = 153
d, (134- 167 + 45 ) - ( 134 + 45 )
= 134 - 167 + 45 - 134 - 45
= ( 134 - 134 ) + ( 45 - 45 ) - 167 = 0 - 0 - 167 = -167
e, 215 + 43 - 215 - 25
= ( 215 - 215 ) + ( 43 - 25 ) = 0 + 18 = 18
f, (-312)- 327 - 28+ 27
= ( -312 - 327 ) - ( 28 - 27 )
= -639 - 1
= -640
a) (2354-45)-2354=2354-45-2354=-45
b) (-2009)-(234-2009)=-2009-234+2009=-234
c) (16+23)+(153-16-23)=16+23+153-16-23=153
d) (134-167+45)-(134+45)=134-167+45-134-45=-167
e) 215+43+(-215)+(-25)=215+43-215-25=18
f) (-312)+(-327)+(-28)+27=-312-327-28+27=-640
TICK và theo dõi mik nhá!
Bài 1 :
a, 169/182 = 169:13 / 182:13 = 13/14
b, 2323/4242 = 2323:101/4242:101 = 23/42
c, 123123/456456 = 123123:3003 / 456456:3003 = 41/152
d,X
Bài 2 :
a, 16/36 = 4/9
20/45 = 4/9
28/63 = 4/9
⇔ 16/36 = 20/45 = 28/63
b,45/65 = 9/13
48/52 = 12/13
2121/1313 = 21/13
⇔ 45/65 < 48/52 < 2121/1313
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