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(x-5)x(1995x1996+1996x1997)=1234x5678x(630-315x2)
(x-5)x[1996x(1995+1997)]=7006652x(630-630)
(x-5)x[1996x3992]=7006652x0
(x-5)x7968032=0
(x-5) =0:7968032
(x-5) =0
x =0+5
x =5
Chúc bn học tốt
#)Giải :
Đặt \(A=\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}\)
\(A=\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}\)
\(A=\frac{1}{5}-\frac{1}{10}\)
\(A=\frac{1}{10}\)
a. 2x +4 (36-x) =100
2x + 144 - 4x = 100
144-100 = 4x - 2x
44=2x
44:2=x
22=x
b. 120 ( x - 9 ) = 90x + 60
120x - 1080 = 90x + 60
120x - 90x = 1080 - 60
30 x = 1020
x = 1020:30
x = 34
\(\frac{2}{3\times5}\times a+\frac{2}{5\times7}\times a+...+\frac{2}{13\times15}\times a=\frac{28}{15}\)
=> \(\left(\frac{2}{3\times5}+\frac{2}{5\times7}+...+\frac{2}{13\times15}\right)\times x=\frac{28}{15}\)
=> \(\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{13}-\frac{1}{15}\right)\times x=\frac{28}{15}\)
=> \(\left(\frac{1}{3}-\frac{1}{15}\right)\times x=\frac{28}{15}\)
=> \(\frac{4}{15}\times x=\frac{28}{15}\)
=> \(x=\frac{28}{15}:\frac{4}{15}\)
-> \(x=7\)
\(\frac{2}{3\times5}\times a+\frac{2}{5\times7}\times a+...+\frac{2}{13\times15}\times a=\frac{28}{15}\)
\(a\times\left(\frac{2}{3\times5}+\frac{2}{5\times7}+...+\frac{2}{13\times15}\right)=\frac{28}{15}\)
\(a\times\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{13}-\frac{1}{15}\right)=\frac{28}{15}\)
\(a\times\left(\frac{1}{3}-\frac{1}{15}\right)=\frac{28}{15}\)
\(a\times\frac{4}{15}=\frac{28}{15}\)
\(a=\frac{28}{15}:\frac{4}{15}\)
\(a=\frac{28}{15}\times\frac{25}{4}\)
\(a=\frac{28}{4}=7\)
a) \(7,3\times x+2,3\times x=25,6\times9,6\)
\(\Rightarrow(7,3+2,3)\times x=245,76\)
\(\Rightarrow9,6\times x=245,76\)
=> x = 25,6
b) x : 4,75 = 31,24 - 25,64
=> x : 4,75 = 5,6
=> x = 26,6
c) \(\frac{3}{4}\times x+\frac{1}{2}\times x-15=35 \)
=> \((\frac{3}{4}+\frac{1}{2})\times x=50\)
=> \(\frac{5}{4}\times x=50\)
=> \(x=40\)
d) \(27,5\times\frac{8.4}{x}\times7=21\)
=> \(\frac{8.4}{x}\times7=\frac{42}{55}\)
=> \(\frac{8.4}{x}=\frac{6}{55}\)
=> x = 77
a)\(28\left(2x+3\right)=196\)
\(\Leftrightarrow56x+84=196\)
\(\Leftrightarrow56x=112\)
\(\Leftrightarrow x=2\)
b)\(28,6+x=30\)
\(\Leftrightarrow x=30-28,6\)
\(\Leftrightarrow x=1,4\)
c)\(2\left(x+2\right)=26\)
\(\Leftrightarrow2x+4=26\)
\(\Leftrightarrow2x=22\)
\(\Leftrightarrow x=11\)
#hoktot<3#
a) \(28\left(2x+3\right)=196\)
\(\Leftrightarrow56x+84=196\)
\(\Leftrightarrow56x=196-84\)
\(\Leftrightarrow56x=112\)
\(\Leftrightarrow x=2\)
b) \(28,6+x=30\)
\(\Leftrightarrow x=30-28,6\)
\(\Leftrightarrow x=1,4\)
c) \(2\left(x+2\right)=26\)
\(\Leftrightarrow2x+4=26\)
\(\Leftrightarrow2x=26-4\)
\(\Leftrightarrow2x=22\)
\(\Leftrightarrow x=11\)