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a) 5.2² - 18 : 3
= 5.4 - 18 : 9
= 20 - 2
= 18
b) 17 . 85 + 15 . 17 - 120
= 17 . (85 + 15) - 120
= 17 . 100 - 120
= 1700 - 120
= 1580
c) 2³ . 17 - 2³ . 14
= 8 . 17 - 8 . 14
= 8 . (17 - 14)
= 8 . 3
= 24
a) 5 . 22 – 18 : 32
= 5.4 – 18 : 9
= 20 – 2
= 18
b) 17 . 85 + 15 . 17 – 120
= 17. (85 + 15) – 120
= 17.100 – 120
= 170 – 120
= 50
c) 23 . 17 – 23 . 14
= 23.(17 - 14)
= 23.3
= 8.3
= 24
a: =35/17-18/17-9/5+4/5
=1-1=0
b: =-7/19(3/17+8/11-1)
=7/19*18/187=126/3553
c: =26/15-11/15-17/3-6/13
=1-6/13-17/3
=7/13-17/3=-200/39
11 + 12 + 13 + 14 + 15 + 16 + 17 + 18 + 19
= (11 + 19) + (12 + 18) + (13 + 17) + (14 + 16) + 15
= 30 + 30 + 30 + 30 + 15
= 120 + 15
= 135
\(11+12+13+14+15+16+17+18+19\)
\(\Leftrightarrow\left(11+19\right)+\left(12+18\right)+\left(13+17\right)+\left(14+16\right)+15\)
\(\Leftrightarrow30+30+30+30+15\)
\(\Leftrightarrow\left(30.4\right)+15\)
\(\Leftrightarrow120+15=135\)
17.85+15.17-120
= 17(85+15)-120
=17.100-120
=1700-120
=1580
A = 12:{ 390 :[500-(125+35.7)]}
A=12:{ 390 :[500-(125+245)]}
A=12:{ 390 :[500-370]}
A=12:{ 390 :130}
A=12:3
A=4
75 - (3.52-4.23)
= 75 - ( 75 - 32)
= 75 - 43
= 32
B = 10+12+14+...+96+98
Tổng trên có số số hạng là:
(98-10):2+1=45 ( số )
\(\Rightarrow\text{B = 10+12+14+...+96+98}=\frac{\left(98+10\right).45}{2}=2430\)
17 . 85 + 15.17 - 120
= 17 ( 85 + 15 ) - 120
= 17 . 100 - 120
= 1700 - 120 = 1580
A = 12 : { 390 : [ 500 - ( 125 + 35 . 7 )]}
A = 12 : { 390 : [ 500 - ( 125 + 245 )]}
A = 12 : { 390 : [ 500 - 370 ]}
A = 12 : { 390 : 130 }
A = 12 : 3 = 4
75 - ( 3 . 52 - 4. 23 )
= 75 - ( 3 . 25 - 4 . 8 )
= 75 - ( 75 - 32 )
= 75 - 75 + 32
= 0 + 32 = 32
B = 10 + 12 + ... + 96 + 98
B có số số hạng là :
( 98 - 10 ) : 2 + 1 = 45 ( số )
B = ( 98 + 10 ) . 45 : 2 = 2430
\(\dfrac{4}{5}\)+\(\dfrac{-5}{4}\)=\(\dfrac{0}{4}\)
\(\dfrac{-1}{3}\)+\(\dfrac{2}{5}-\dfrac{5}{6}\)=\(\dfrac{-10}{30}+\dfrac{12}{30}-\dfrac{25}{30}\)=\(\dfrac{-23}{30}\)
\(\dfrac{2}{3}-\dfrac{5}{7}.\dfrac{14}{25}\)=\(\dfrac{2}{3}-\dfrac{2}{5}\)=\(\dfrac{10}{15}-\dfrac{6}{15}\)=\(\dfrac{4}{15}\)
a)5*2^2-18:3=20-6=14
b)17*85+15*17-120=17*(120-85+15)=17*20=340
c2^3*17-2^3*14=2^3(17-14)=8*3=24
\(1\dfrac{14}{15}-\dfrac{5}{17}-\dfrac{12}{17}-\dfrac{14}{15}\\ =\left(1\dfrac{14}{15}-\dfrac{14}{15}\right)-\left(\dfrac{5}{17}+\dfrac{12}{17}\right)\\ =\left[1+\left(\dfrac{14}{15}-\dfrac{14}{15}\right)\right]-1=1-1=0\)