hiu hiu giải giúp tớ mấy câu này với ạ:33
1,
a, 315+(135- x) =450
b, 442 + (418 - x) = 860
2,
a,18:3 + 182+3.(51:7)
b, 12: [ 400 : [ 500 - (125 +25 .7] ]
c, 13.17 - 256 : 16 +14:7 -1
d, 22+23+24+... +27+28
e, 99-97+95-93+91-89+...+7-5_3-1
g, 98-96+94-92+90-88+...+10-8+6-4
f,274- (9x +18)=4
h,442+(418- x) 860
3,
a, 155 - 10 (x+1) = 55
b, 14x+54=82
c, 15x-133=17
3,
210 - 5x = 200
210-:x-10 =20
210 - 5 ( x-10) = 200
(5x - 39) .7+3=80
4,
a, 400- x.3 = 100
b, 250 : x+ 10=20
c, 96-3 . (x +8) = 42
d,15 . 5 (x -35 ) - 525 = 0
e,[3 . (70 - x ) +5 ] :2 = 46
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![](https://rs.olm.vn/images/avt/0.png?1311)
39/5 + ( 9/4 - 9/5 ) - ( 5/4 + 6/7 )
= 39/5 + 9/20 - 59/28
= 33/4 - 59/28
= 43/7
![](https://rs.olm.vn/images/avt/0.png?1311)
mk ko nghi lại đề nx nhé.
= { [ ( -0,56)2 : 49/125 ] . 5/6 } - ( 1/6 )
=( 0,8 . 5/6) - 1/6
= ( 8/10 . 5/6 ) - 1/6
= ( 4/5 . 5/6 ) - 1/6
= 2/3 - 1/6
= 1/2
=\(\left\{\left[\left(\dfrac{1}{25}-\dfrac{3}{5}\right)^2:\dfrac{49}{125}\right].\dfrac{5}{6}\right\}-\left[\left(\dfrac{-2}{6}\right)+\dfrac{3}{6}\right]\)
\(=\left\{\left[\left(\dfrac{1}{25}-\dfrac{15}{25}\right)^2:\dfrac{49}{125}\right].\dfrac{5}{6}\right\}-\dfrac{1}{6}\)
\(=\left\{\left[\left(\dfrac{-14}{25}\right)^2:\dfrac{49}{125}\right].\dfrac{5}{6}\right\}-\dfrac{1}{6}\)
\(=\left\{\left[\dfrac{196}{625}.\dfrac{125}{49}\right].\dfrac{5}{6}\right\}-\dfrac{1}{6}\)
\(=\left\{\dfrac{4}{5}.\dfrac{5}{6}\right\}-\dfrac{1}{6}\)
\(=\dfrac{2}{3}-\dfrac{1}{6}\)
\(=\dfrac{4}{6}-\dfrac{1}{6}\)
\(=\dfrac{3}{6}=\dfrac{1}{2}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
2/7>9/49
3/8>4/72
5/6>1/42
5/12>7/36
4/9>7/54
So sánh 2 phân số:
\(\dfrac{2}{7}\) và \(\dfrac{9}{49}\)
\(\dfrac{2}{7}=\dfrac{2\times49}{7\times49\text{}}=\dfrac{98}{343}\)
\(\dfrac{9}{49}=\dfrac{9\times7}{49\times7}=\dfrac{63}{343}\)
Vì: 98 > 63
Nên: \(\dfrac{2}{7}>\dfrac{9}{49}\)
\(\dfrac{3}{8}\) và \(\dfrac{4}{72}\)
\(\dfrac{3}{8}=\dfrac{3\times72}{8\times72}=\dfrac{216}{576}\\ \dfrac{4}{72}=\dfrac{4\times8}{72\times8}=\dfrac{32}{576}\)
Vì: 216 > 32
Nên: \(\dfrac{3}{8}>\dfrac{4}{72}\)
\(\dfrac{5}{6}\) và \(\dfrac{1}{42}\)
\(\dfrac{5}{6}=\dfrac{5\times42}{6\times42}=\dfrac{210}{252}\\ \dfrac{1}{42}=\dfrac{1\times6}{42\times6}=\dfrac{6}{252}\)
Vì: \(210>6\)
Nên: \(\dfrac{5}{6}>\dfrac{1}{42}\)
\(\dfrac{5}{12}\) và \(\dfrac{7}{36}\)
\(\dfrac{5}{12}=\dfrac{5\times36}{12\times36}=\dfrac{180}{432}\\ \dfrac{7}{36}=\dfrac{7\times12}{36\times12}=\dfrac{84}{432}\)
Vì: 180 > 84
Nên: \(\dfrac{5}{12}>\dfrac{7}{36}\)
\(\dfrac{4}{9}\) và \(\dfrac{7}{54}\)
\(\dfrac{4}{9}=\dfrac{4\times54}{9\times54}=\dfrac{216}{486}\\ \dfrac{7}{54}=\dfrac{7\times9}{54\times9}=\dfrac{63}{486}\)
Vì: 216 > 63
Nên: \(\dfrac{4}{9}>\dfrac{7}{54}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
ụa toán mà:v