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5 x X - 8 - 22
5 x X = 22 + 8
5 x X = 30
X = 30 : 5
X = 6
Chúc bạn học tốt!!!
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\(\dfrac{\dfrac{22}{15}}{11-x}\) + \(\dfrac{2}{3}\) = \(\dfrac{7}{5}\)
\(\dfrac{\dfrac{22}{15}}{11-x}\) = \(\dfrac{7}{5}\) - \(\dfrac{2}{3}\)
\(\dfrac{\dfrac{22}{15}}{11-x}\) = \(\dfrac{11}{15}\)
11 - \(x\) = \(\dfrac{22}{15}\) : \(\dfrac{11}{15}\)
11 - \(x\) = 2
\(x\) = 11 - 2
\(x\) = 9
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Bài 2:
a, \(\dfrac{5}{23}\) \(\times\) \(\dfrac{17}{26}\) + \(\dfrac{5}{23}\) \(\times\) \(\dfrac{9}{26}\)
= \(\dfrac{5}{23}\) \(\times\) ( \(\dfrac{17}{26}\) + \(\dfrac{9}{26}\))
= \(\dfrac{5}{23}\) \(\times\) \(\dfrac{26}{26}\)
= \(\dfrac{5}{23}\)
b, \(\dfrac{3}{4}\) \(\times\) \(\dfrac{7}{9}\) + \(\dfrac{7}{4}\) \(\times\) \(\dfrac{3}{9}\)
= \(\dfrac{7}{12}\) + \(\dfrac{7}{12}\)
= \(\dfrac{14}{12}\)
= \(\dfrac{7}{6}\)
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Ta có \(VP=\frac{\left(20+29\right)\times10}{2}=245\)
=> 20xX+45=245
20xX=200
X=10
20.x + 45 = 20 + 21 + 22 + ... + 29
=> 20.x + 45 = (29 + 20).[(29 - 20) : 1 + 1] : 2
=> 20.x + 45 = 49 . 10 : 2
=> 20.x + 45 = 245
=> 20.x = 245 - 45
=> 20.x = 200
=> x = 200 : 20
=> x =10
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a) \(1010+1111+1212+.....+9898+9999\)\(=\frac{\left(1010+9999\right)\cdot\left(\frac{9999-1010}{1111-1010}+1\right)}{2}\)\(=\frac{11009\cdot\left(\frac{8989}{101}+1\right)}{2}\)\(=\frac{11009\cdot\left(89+1\right)}{2}\)\(=\frac{11009\cdot90}{2}\)\(=\frac{990810}{2}\)\(=495405\)
a) Khoảng cách của dãy số là:
1111-1010=101;1212-1111=101;...
Số số hạng của dãy số là:
(9999-1010):101+1=90(số)
Tổng:
(1010+9999)*90:2=495405
Đ/s:495405
Nhớ k mk nha!
[X-15]:5=22-22=2
[X-15]=2*5=10
X=10+15
X=25
( x - 15 ) : 5 + 20 = 22
( x - 15 ) : 5 = 22 - 20
( x - 15 ) : 5 = 2
( x - 15 ) = 2 . 5
x - 15 = 10
x = 10 + 15
=> x = 25