390×5=?
Kết quả của phép tính (-2) . (-13) . (-5) . 3 là: (Chỉ được chọn 1 đáp án)
A.-100 .
B.390 .
C.-17 .
D.. -390 .
a) 15:{390:[ 5³.4 – (5. 2⁵+35.6)]}
thank
\(=15:\left\{390:\left[125\cdot4-5\cdot32-210\right]\right\}\)
\(=15:\left\{390:130\right\}=15:3=5\)
=> 15:{390:[125.4-(5.32+210)]}
=> 15:{390:[500-(160+210)]}
=> 15:{390:[500-370]}
=> 15:{390:130}
=> 15:3=5
15 : {390 : [125.4 - (5.32 + 210)]}
15 : {390 : [500 - (160 + 210)]}
15 : {390 : [500 - 370]}
15 : {390 : 130}
15 : 3 = 5
15 : { 390 : [ 5^3 .4 - ( 5.2^5 + 35 . 6 ) ] }
=15 : { 390 : [ 125.4 - ( 5.32 + 35 . 6 ) ] }
=15 : { 390 : [ 500 - ( 160 + 35 . 6 ) ] }
=15 : { 390 : [ 500 - ( 160 + 210 ) ] }
=15 : { 390 : [ 500 - 370 ] }
=15 : { 390 : 130 }
= 15: 3
= 5
45 /{390/[5*100-(125 +49+5)]}
\(45:\left\{390:\left[5.100-\left(125+49+5\right)\right]\right\}\)
\(=45:\left\{390:\left[500-179\right]\right\}\)
\(=45:\left\{390:321\right\}\)
\(=45:\dfrac{130}{107}\)
\(=\dfrac{963}{26}\)
tìm x:
390 : ( 5x - 5 ) = 39
\(\dfrac{390}{5x-5}=39\left(ĐK:x\ne1\right)\)
<=> \(5x-5=10\)
<=> \(5x=15\)
<=> \(x=3\left(TM\right)\)
(Mik viết ra phân số luôn cho gọn nhé.)
390 : ( 5x - 5 ) = 39
5x - 5 =390:39
5x - 5 =10
5x =10-5
5x = 5
x =5:5
x =1
Vậy x=1
`390 : (5x-5)=39`
`<=> 5x-5 = 390:39`
`<=> 5x-5=10`
`<=> 5x = 10 + 5`
`<=> 5x = 15`
`<=> x = 15 : 5`
`<=> x = 3`
24:{390:[500-(5^3+49.5)]}
\(24:\text{ }\left\{390:\text{ }\left[500-\left(5^3+49.5\right)\right]\right\}\)
\(=24:\left\{390:\left[500-\left(125+245\right)\right]\right\}\)
\(=24:\text{ }\left\{390:\left[500-370\right]\right\}\)
\(=24:\left\{390:130\right\}\)
\(=24:3\)
\(=8\)
12 :{390:[2.5^2-(5^3+7^2.5)]}
Cho S=5+5 mũ 2+5 mũ 3+...+5 mũ 2012.chứng tỏ S chia hết cho 390
[x+1]+[x+2]+[x+3]+[x+4]+[x+5]...=390