A=(12+22+......+1002)(279*68-11*17*108)=?
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\(\dfrac{21}{11}\times\dfrac{22}{17}\times\dfrac{68}{63}\) = \(\dfrac{42}{17}\times\dfrac{68}{63}\) = \(\dfrac{8}{3}\)
Vì \(\dfrac{21}{11}\times\dfrac{22}{17}=\dfrac{21\times22}{11\times17}=\dfrac{42}{17}\)
Vậy:
\(\dfrac{21}{11}\times\dfrac{22}{17}\times\dfrac{63}{68}\) =\(\dfrac{42}{17}\times\dfrac{68}{63}\) =\(\dfrac{21\times2\times17\times4}{17\times21\times3}\) =\(\dfrac{8}{3}\) =
a, = 21.22.68 / 11.17.63
= 21. 22 .68 / 11.22.21.3
=68 / 33
b, =5.7.26 / 14.13.25
= 5 . 7 .13 .2/ 7 . 2.13. 5.5
= 1/5
\(\dfrac{21}{11}\times\dfrac{22}{17}\times\dfrac{68}{63}:\dfrac{4}{3}=\dfrac{21}{11}\times\dfrac{22}{17}\times\dfrac{68}{63}\times\dfrac{3}{4}=\dfrac{462}{187}\times\dfrac{204}{252}=\dfrac{42}{17}\times\dfrac{17}{21}=\dfrac{2}{1}=2\)
21/11 x 22/17 x 68/63 : 4/3
=( 21/11 x 22/17) x (68/63 : 4/3)
= 42/17 x 17/21
= 2/1 = 2
c) (3x + 11) : 8 = 46
=> 3x + 11 = 368
=> 3x = 368 - 11
=> 3x = 357
=> x = 357 : 3
=> x = 119
b) 100 + (x - 23) = 317
=> x - 23 = 317 - 100
=> x - 23 = 217
=> x = 217 + 23
=> x = 240
a) 1002 : (x - 12) = 3
=> x - 12 = 1002 : 3
=> x - 12 = 334
=> x = 334 + 12
=> x = 346
d) 68 - 4x = 24
=> 4x = 68 - 24
=> 4x = 44
=> x = 44 : 4 = 11
e) 110 - (4x + 15) = 3
=> 4x + 15 = 110 - 3
=> 4x + 15 = 107
=> 4x = 107 - 15
=> 4x = 92
=> x = 92 : 4 = 23