![](https://rs.olm.vn/images/avt/0.png?1311)
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(\dfrac{1}{1.3}+\dfrac{1}{3.5}+...+\dfrac{1}{13.15}\right).x=\dfrac{-26}{45}\\ \Leftrightarrow\left(\dfrac{2}{1.3}+\dfrac{2}{3.5}+...+\dfrac{2}{13.15}\right).x=\dfrac{-52}{45}\\ \Leftrightarrow\left(1-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+...+\dfrac{1}{13}-\dfrac{1}{15}\right).x=\dfrac{-52}{45}\\ \Leftrightarrow\left(1-\dfrac{1}{15}\right).x=\dfrac{-52}{45}\\ \Leftrightarrow\dfrac{14}{15}.x=\dfrac{-52}{45}\\ \Leftrightarrow x=-\dfrac{26}{21}\)
(11.3+13.5+...+113.15).x=−2645⇔(21.3+23.5+...+213.15).x=−5245⇔(1−13+13−15+...+113−115).x=−5245⇔(1−115).x=−5245⇔1415.x=−5245⇔x=−2621
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a,x+2010=2021\\ \Rightarrow x=2021-2010\\ \Rightarrow x=11\\ b,x^5=32\\ \Rightarrow x^5=2^5\\ \Rightarrow x=2\\ c,2^x=16\\ \Rightarrow2^x=2^4\\ \Rightarrow x=4\\ d,4.2^x-3=125\\ \Rightarrow4.2^x=128\\ \Rightarrow2^x=32\\ \Rightarrow2^x=2^5\\ \Rightarrow x=5\\ e,3^x+3^{x+1}=324\\ \Rightarrow3^x+3^x.3=324\\ \Rightarrow\left(1+3\right).3^x=324\\ \Rightarrow4.3^x=324\\ \Rightarrow3^x=81\\ \Rightarrow3^x=3^4\\ \Rightarrow x=4\)
a, <=> x= 11
b, <=> x5 =25
<=> x=2
c, <=> 2x =24
<=> x=4
d, 4.2x -3 =125
<=> 4.2x =128
<=> 2x = 32
<=>2x = 25
<=> x=5
e, <=> 3x +3x.3=324
<=> 4.3x =324
<=> 3x =81
<=> 3x =34
<=> x=4
![](https://rs.olm.vn/images/avt/0.png?1311)
\(2x+7⋮x+2\)
\(\Leftrightarrow x+2\in\left\{1;-1;3;-3\right\}\)
hay \(x\in\left\{-1;-3;1;-5\right\}\)
\(\Rightarrow2\left(x+2\right)+3⋮x+2\\ \Rightarrow x+2\inƯ\left(3\right)=\left\{-3;-1;1;3\right\}\\ \Rightarrow x\in\left\{-5;-3;-1;1\right\}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
<=> 2x^2 +x-4x-2-5x-15=2x^2-6x+4+8x-2-2x
2x^2-8x-17-2x^2-2=0
-8x-19=0
x=-19/8
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Gọi số học sinh khối 6 là x
Theo đề, ta có: \(x-3\in BC\left(8;12;15\right)\)
\(\Leftrightarrow x-3\in\left\{120;240;360;...\right\}\)
\(\Leftrightarrow x\in\left\{123;243;363\right\}\)
mà 200<=x<=300
nên x=243
Gọi số học sinh khối 6 là a
a + 3 \(⋮8;12;15\)
\(\Rightarrow\) \(a+3\in BC\left(8;12;15\right)\)
8 = 2 . 3
12 = 22 . 3
15 = 3 . 5
\(\Rightarrow\) BCNN (8; 12; 15) = 22 . 3 . 5 = 60
Mà 203 < a + 3 < 303 học sinh
\(\Rightarrow\) a + 3 \(\in\) {240; 300}
\(\Rightarrow\) a \(\in\) {237; 207}
![](https://rs.olm.vn/images/avt/0.png?1311)
Số trứng người đó mang ra chợ là:
\(54:\dfrac{3}{5}=54\cdot\dfrac{5}{3}=90\left(quả\right)\)
Trả lời:
D. ( 3101 - 1 ) : 2
~HT~
Đáp án D nha