Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
a, ((2.x+54)-32).2=244
((2.x+54)-32)=244:2
((2.x+54)-32)=122
(2.x+54)=122+32
(2.x+54)=154
x+54=154:2
x+54=77
x=77-54
x=23
\(12< x< y< 16\)
để \(12< x< 16\Leftrightarrow x\in\left\{13;14;15\right\}\)
nếu \(x=13\Leftrightarrow y=\left\{14;15\right\}\)(t/m đk)
nếu \(x=14\Leftrightarrow y=\left\{15\right\}\) (t/m đk )
nếu \(x=15\Leftrightarrow y=\left\{\varnothing\right\}\)
vậy để \(112< x< y< 16\) thì \(x=\left\{13,14\right\}\) ; \(y=\left\{14;15\right\}\)
\(a,\dfrac{7}{12}-\left(x+\dfrac{7}{10}\right):\dfrac{6}{5}=\dfrac{5}{4}\)
\(\Leftrightarrow\dfrac{7}{12}-x-\dfrac{7}{10}:\dfrac{6}{5}=\dfrac{5}{4}\)
\(\Leftrightarrow\dfrac{7}{12}-x-\dfrac{7}{12}=\dfrac{5}{4}\)
\(\Leftrightarrow\dfrac{7}{12}-x=\dfrac{5}{4}+\dfrac{7}{12}\)
\(\Leftrightarrow\dfrac{7}{12}-x=\dfrac{11}{6}\)
\(\Leftrightarrow x=\dfrac{7}{12}-\dfrac{11}{6}\)
\(\Leftrightarrow\dfrac{-5}{4}\)
1.A= 1.2.3+2.3.4+...+29.30.31+x=15
\(4A=1.2.3.4+2.3.4.\left(5-1\right)+...+29.30.31.\left(32-28\right)+4x=60\)
\(\Rightarrow4A=1.2.3.4+2.3.4.5-1.2.3.4+...+29.30.31.32-28.29.30.31+4x=60\)
Từ đó suy ra nha bạn
2.\(\frac{2}{2.3}+\frac{2}{3.4}+...+\frac{2}{x\left(x+1\right)}=\frac{2007}{2009}\)
\(=\frac{2}{2\left(2+1\right)}+\frac{2}{3.\left(3+1\right)}+...+\frac{2}{x\left(x+1\right)}=\frac{2007}{2009}\)
\(=2.\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{x}-\frac{1}{x+1}\right)=\frac{2007}{2009}\)
\(=2.\left(\frac{1}{2}-\frac{1}{x+1}\right)=\frac{2007}{2009}\\ =1-\frac{2}{\left(x+1\right)}=\frac{2007}{2009}\)
\(\Rightarrow\frac{2}{x+1}=\frac{2}{2009}\Rightarrow x+1=2009\Rightarrow x=2008\)
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20=210
1+2+3+4+5+6+7=28
a)dãy trên có 20 số hạng , vậy tổng là:
(20 + 1) x 20 : 2 = 210
b) làm tương tự bài a
\(\frac{2}{10}x+\frac{3}{10}x=2,5\)
\(\frac{2}{10}x+\frac{3}{10}x=\frac{5}{2}\)
\(x\cdot\left(\frac{2}{10}+\frac{3}{10}\right)=\frac{5}{2}\)
\(x\cdot\frac{1}{2}=\frac{5}{2}\)
\(x=\frac{5}{2}:\frac{1}{2}\)
\(x=\frac{5}{2}\cdot\frac{2}{1}\)
\(x=5\)
10x + 22 x 5 = 10
=> 10x + 4 x 5 = 10
=> 10x + 20 = 10
=> 10x = 10 - 20
=> 10x = -10
=> x = -10 : 10
=> x = -1.
Vậy: x = -1.
10x+2 mủ 2x5=10
10x+20=10
10x=20-10
10x=10
x=10:10
x=1
mình ko chắc lắng nhưng
bye
1.
1.2 +2.3 +...+97.98
=1/3.(1.2.3 +2.3.3 +3.4.3 +...+97.98.3)
=1/3.(1.2.3 - 0.1.2+ 2.3.4 -1.2.3 + 3.4.5 -2.3.4 + ... +97.98.99 -96.97.98)
=1/3 . 97.98.99
= 313698
=>1.2 +2.3 +...+97.98-x=16
=>313698-x=16
=> x=313682
4.
\(\left[\left(\frac{36}{x}-x\right):x-x\right]:x-x=-x\)
\(\left[\left(\frac{36}{x}-x\right):x-x\right]:x=-x+x\)
\(\left[\left(\frac{36}{x}-x\right):x-x\right]:x=0\)
\(\left[\left(\frac{36}{x}-x\right):x-x\right]=0\)
\(\left(\frac{36}{x}-x\right):x=x\Rightarrow\frac{36}{x}-x=x^2\)
\(\frac{36}{x}=x^2+x=x\left(x+1\right)\Rightarrow36=x^2\left(x+1\right)\)
Mà Ư(36)={1;2;3;4;6;9;12;18;36}; 9 là số chính phương duy nhất bé hơn 36=> x2 = 9 => x=3
2 câu kia thì đợi một lúc.
\(10+2x=16\)
\(2x=16-10\)
\(2x=6\)
\(x=3\)
vay \(x=3\)
\(720:\left[41-\left(2x-5\right)\right]=40\)
\(720:\left(41-2x+5\right)=40\)
\(46-2x=720:40\)
\(46-2x=18\)
\(2x=46-18\)
\(2x=28\)
\(x=14\)
vay \(x=14\)
a) <=> 2x=6
<=>x=3
b)41-(2x-5)=18
<=>2x-5=23
2x=28
x=14
mk ko ghi đề nha chúc bn học tốt