\(\frac{18}{31}\)x\(\frac{62}{21}\)
\(\frac{18}{31}\)x\(\frac{62}{21}\)
18/31 x 62/21 = 18x62/31x21 = 3x6x31x2/31x3x7=6x2/7=12/7
\(\frac{18}{31}.\frac{62}{21}=\frac{18.62}{31.21}=\frac{3.6.31.2}{31.3.7}=\frac{6.2}{7}=\frac{12}{7}\)
\(\frac{18}{31}\)x\(\frac{62}{21}\)=\(\frac{12}{7}\)
Tìm x biết
\(\frac{1}{4}.\frac{2}{6}.\frac{3}{8}.\frac{4}{10}......\frac{30}{62}.\frac{31}{62}=2^x\)
\(\frac{1}{4}.\frac{2}{6}............\frac{31}{64}=2^x\)
\(\Rightarrow\frac{1.2........31}{2.2.2.3...........2.31.64}=2^x\)
\(\Rightarrow\frac{1}{2^{30}.2^4}=2^x\)
\(\Rightarrow\frac{1}{2^{34}}=2^x\)
\(\Rightarrow x=-34\)
Tính nhanh:
a) N= \(\frac{18\times275+3\times666+9\times614\times2}{1+4+7+...+58+61+62+62\times2+62\times3+62\times4-271}\).
b) M=( 1- \(\frac{1}{3}\))x( 1- \(\frac{1}{6}\))x( 1- \(\frac{1}{10}\))x( 1- \(\frac{1}{10}\))x( 1- \(\frac{1}{15}\))x( 1- \(\frac{1}{21}\))x( 1- \(\frac{1}{28}\)).
N=( \(\frac{6}{8}\)+ 1)x( \(\frac{6}{18}\)+ 1)x( \(\frac{6}{30}\)+ 1)x...x( \(\frac{6}{10100}\)+ 1).
\(4\frac{5}{9}:2\frac{5}{18}-7< x< \left(3\frac{1}{5}:3,2+4,5\cdot1\frac{31}{45}\right)=\left(-21\frac{1}{2}\right)\)
tìm x
\(4\frac{5}{9}:2\frac{5}{18}-7< x< \left(3\frac{1}{5}:3,2+4,5\times1\frac{31}{45}\right):\left(-21\frac{1}{2}\right)\)
Tính lần lượt 2 vế ta được:
-5 < x< -0,4
=> x = -4, -3, -2, -1, 0
Tìm \(x\in Z\) : \(4\frac{5}{9}\div2\frac{5}{18}-7< x< \left(3\frac{1}{3}\div3,2+4,5\times1\frac{31}{45}\right)\div\left(-21\frac{1}{2}\right)\)
\(\Leftrightarrow-5< x< -\dfrac{1037}{1260}\)
=>\(x\in\left\{-4;-3;-2;-1\right\}\)
Tìm tập hợp các số nguyên x biết rằng:
\(4\frac{5}{9}:2\frac{5}{18}< x< \left(3\frac{1}{5}.3,2+4,5.1\frac{31}{45}\right):\left(-21\frac{1}{2}\right)\)
Giúp nha gấp lắm
Tham khảo :
Câu hỏi của Lê Huyền Trang - Toán lớp 7 - Học trực tuyến OLM
Tìm x biết:\(\frac{1}{4}.\frac{2}{6}.\frac{3}{8}...\frac{30}{62}.\frac{31}{64}=2^x\)
\(\frac{1}{4}\cdot\frac{2}{6}\cdot\frac{3}{8}\cdot......\cdot\frac{31}{64}=2^x\)
\(\Leftrightarrow\frac{1\cdot2\cdot3\cdot....\cdot31}{4\cdot6\cdot8\cdot....\cdot64}=2^x\)
\(\Leftrightarrow\frac{1\cdot2\cdot3\cdot....\cdot31}{\left(2\cdot2\right)\cdot\left(3\cdot2\right)\cdot\left(4\cdot2\right)\cdot.....\cdot\left(2\cdot32\right)}=2^x\)
\(\Leftrightarrow\frac{1\cdot2\cdot3\cdot...\cdot31}{\left(2\cdot2\cdot2\cdot....\cdot2\right)\left(1\cdot2\cdot3\cdot.....\cdot31\right)\cdot32}=2^x\)
\(\Leftrightarrow\frac{1}{2^{31}.2^5}=2^x\)
\(\Leftrightarrow\frac{1}{2^{36}}=2^x\)
\(\Rightarrow x=-36\)
trong các phân số \(\frac{31}{52},\frac{31}{62},\frac{31}{72},\frac{31}{82}\)phân số chưa tối giản là
A.\(\frac{31}{52}\)
B.\(\frac{31}{62}\)
C.\(\frac{31}{72}\)
D. Không có
Phân số chưa được tối giản là: B.\(\frac{31}{62}\)