x+14=20-5

x+14=15

x=15-14

x=1

\(20-\left(x+14\right)=5\)

\(\Rightarrow x+14=20-5=15\)

\(\Rightarrow x=15-14\)

\(\Rightarrow x=1\)

a)1999*2000-1:1998+1999*2000=[(1999*2000)-(1999*2000)] va 1:1998

                                                     =0 + 1998

                                                     =1998 

B=\(\left[\left(\frac{1}{3}+\frac{1}{4}\right)x\frac{12}{19}+\frac{12}{19}\right]:\frac{4}{5}-\frac{1}{4}+2012\)

B=\(\left(\frac{7}{12}x\frac{12}{19}+\frac{12}{19}\right):\frac{4}{5}-\frac{1}{4}+2012\)

B=\(\left(\frac{7}{19}+\frac{12}{19}\right):\frac{4}{5}-\frac{1}{4}+2012\)

B=\(\frac{5}{4}-\frac{1}{4}+2012\)

B=1+2012

B=2013

\(B=[\left(\frac{1}{3}+\frac{1}{4}\right)\times\frac{12}{19}+\frac{12}{19}]:\frac{4}{5}-\frac{1}{4}+2012\)

\(B=[\frac{7}{12}\times\frac{12}{19}+\frac{12}{19}]:\frac{4}{5}-\frac{1}{4}+2012\)

\(B=[\frac{7}{19}+\frac{12}{19}]:\frac{4}{5}-\frac{1}{4}+2012\)

\(B=1:\frac{4}{5}-\frac{1}{4}+2012\)

\(B=\frac{5}{4}-\frac{1}{4}+2012\)

\(B=1+2012\)

\(B=2013\)

do 5 chia hết cho5 nên 2 x 3 x 4 x 5 x 7 x 9 x 2013 chia hết cho 5

hay A chia hết cho 5

suy ra A + 1 CHIA 5 DƯ 1

a) 2 x 3 x 4 x 8 x 50 x 25 x 125

= (2 x 50) x ( 4 x 25 ) x (8 x 125) x 3 = 100 x 100 x 1000 x 3

= 30 000 000

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a ) 11 x 62 - 12 x 11 + 50 x 11

= 11 x ( 62 - 12 + 50 )

= 11 x 100 

= 1100

b ) 1996 + 3992 + 5988 + 7984

= ( 1996 + 7984 ) + ( 3992 + 5988 )

= 9980 + 9980

= 9980 x 2 

= 19 960

a, 11 x 62 - 12 x 11 + 50 x 11

= 11 x ( 62 - 11 + 50 )

= 11 x 101

= 1111

b, 1996 + 3992 + 5988 + 7984

=( 1996 + 7984 ) + ( 3992 + 5988 )

= 9980 + 9980

= 19960

a ) 5^x-2 - 3² = 2⁴ - ( 2⁸ . 2⁴ - 2¹⁰ . 2² )

5^x-2 - 9 = 16 - ( 256 . 16 - 1024 . 4 ) 

5^x-2 - 9 = 16 - ( 4096 - 4096 ) = 16 - 0

5^x-2 = 16 + 9 = 25  nhưng\(\sqrt{25}=5^2\)x = 2 + 2 = 4

b ) b ) 697 : [( 15 x + 364 ) : x ] = 17

mình ko hiểu đề cho lắm