2^x+1.4^2=16
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MA
3 tháng 2 2022
1.
`16 + (27 - 7.6 ) - (94 -7 - 27.99)`
`= 16+ 27 - 7.6 - 94 + 7 + 27.99`
`= 16 + 27(99 +1) - 7(6-1) - 94`
`= -78 + 27.100 - 7.5`
`= 2587`
2.
`A = 2/1.4 + 2/4.7 + 2/7.10 +...+ 2/97.100`
`A= 2(1/1.4 + 1/4.7 + 1/7.10 +...+1/97.100)`
`3A = 2 (3/1.4 + 3/4.7 + 3/7.10+...+ 3/97.100)`
`3/2 A = 1 - 1/4 + 1/4 - 1/7 +...+ 1/97 - 1/100`
`3/2A = 1 - 1/100`
`3/2 A= 99/100`
`A= 99/100 : 3/2`
`A=33/50`
Vậy `A= 33/50`
TD
3 tháng 2 2022
1.16+(27-7.6)-(94-7-27.99)=16+27-7.6-94+7+27.99
=(27+27.99)+(27+7-94)+16
=27.100-60+16
=2700-44=2656
2.A=\(\dfrac{2}{1.4}+\dfrac{2}{4.7}+\dfrac{2}{7.10}+...+\dfrac{2}{97.100}\)
=\(\dfrac{1}{1}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+...+\dfrac{1}{97}-\dfrac{1}{100}\)
=\(1-\dfrac{1}{100}=\dfrac{99}{100}\)
1 tháng 9 2016
a) \(16+\left(27-7\cdot6\right)-\left(94\cdot7-27\cdot99\right)\)
\(=16+27-7\cdot6-94\cdot7+27\cdot99\)
\(=16+27\left(1+99\right)-7\left(6+94\right)=16+2700-700=2016\)
b)\(A=\frac{2}{1\cdot4}+\frac{2}{4\cdot7}+\frac{2}{7\cdot10}+...+\frac{2}{97\cdot100}\)
\(=\frac{1}{3}\left(\frac{2}{1}-\frac{2}{4}+\frac{2}{4}-\frac{2}{7}+\frac{2}{7}-\frac{2}{10}+...+\frac{2}{97}-\frac{2}{100}\right)\)
\(=\frac{1}{3}\left(2-\frac{2}{100}\right)=\frac{1}{3}\cdot\frac{99}{50}=\frac{33}{50}\)
3 tháng 2 2019
\(A=\frac{2}{1.4}+\frac{2}{4.7}+\frac{2}{7.10}+...+\frac{2}{97.100}\)
\(A=2\left(\frac{1}{1.4}+\frac{1}{4.7}+\frac{1}{7.10}+...+\frac{1}{97.100}\right)\)
\(A=2\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{97}-\frac{1}{100}\right)\)
\(A=2\left(1-\frac{1}{100}\right)\)
\(A=2.\frac{99}{100}=..............\)
Tự làm nốt nha
29 tháng 12 2017
a,\(\dfrac{x+1}{65}+\dfrac{x+2}{64}=\dfrac{x+3}{63}+\dfrac{x+4}{62}\)
\(\Rightarrow\dfrac{x+1}{65}+1+\dfrac{x+2}{64}+1=\dfrac{x+3}{63}+1+\dfrac{x+4}{62}\)
\(\Rightarrow\dfrac{x+1+65}{65}+\dfrac{x+2+64}{64}=\dfrac{x+3+63}{63}+\dfrac{x+4+62}{62}\)
\(\Rightarrow\dfrac{x+66}{65}+\dfrac{x+66}{64}-\dfrac{x+66}{63}-\dfrac{x+66}{62}=0\)
\(\Rightarrow\left(x+66\right)\left(\dfrac{1}{65}+\dfrac{1}{64}-\dfrac{1}{63}-\dfrac{1}{62}\right)=0\)
\(\Rightarrow x+66=0\) ( vì \(\dfrac{1}{65}+\dfrac{1}{64}-\dfrac{1}{63}-\dfrac{1}{62}>0\) )
\(\Rightarrow x=-66\)
\(b,\dfrac{x-12}{77}+\dfrac{x-11}{78}=\dfrac{x-74}{15}+\dfrac{x-73}{16}\)
\(\Rightarrow\dfrac{x-12}{77}-1+\dfrac{x-11}{78}-1=\dfrac{x-74}{15}-1+\dfrac{x-73}{16}-1\)
\(\Rightarrow\dfrac{x-12-77}{77}+\dfrac{x-11-78}{78}=\dfrac{x-74-15}{15}+\dfrac{x-73-16}{16}\)
\(\Rightarrow\dfrac{x-89}{77}+\dfrac{x-89}{78}-\dfrac{x-89}{15}-\dfrac{x-89}{16}=0\)
\(\Rightarrow\left(x-89\right)\left(\dfrac{1}{77}+\dfrac{1}{78}-\dfrac{1}{15}-\dfrac{1}{16}\right)=0\)
\(\Rightarrow x-89=0\)
\(\Rightarrow x=89\)
NT
29 tháng 12 2017
b.
\(\dfrac{x-12}{77}+\dfrac{x-11}{78}=\dfrac{x-74}{15}+\dfrac{x-73}{16}\\ \Rightarrow\left(\dfrac{x-12}{77}-1\right)+\left(\dfrac{x-11}{78}-1\right)=\left(\dfrac{x-74}{15}-1\right)+\left(\dfrac{x-73}{16}-1\right)\\ \Leftrightarrow\dfrac{x-89}{77}+\dfrac{x-89}{78}=\dfrac{x-89}{15}+\dfrac{x-89}{16}\\ \Leftrightarrow\dfrac{x-89}{77}+\dfrac{x-89}{78}-\dfrac{x-89}{15}-\dfrac{x-89}{16}=0\\ \\ \Leftrightarrow\left(x-89\right)\left(\dfrac{1}{77}+\dfrac{1}{78}-\dfrac{1}{15}-\dfrac{1}{16}\right)=0\\ \Leftrightarrow x-89=0\\ \Leftrightarrow x=89\)
29 tháng 8 2018
Ta có : (12+13+14+....+110)×x=19+28+....+82+91(12+13+14+....+110)×x=19+28+....+82+91
Đặt A=19+28+....+82+91A=19+28+....+82+91
=(9−1−1−....−1)+(82+1)+(73+1)+.....+(19+1)=(9−1−1−....−1)+(82+1)+(73+1)+.....+(19+1)
=1+102+103+...+109=102+103+....+109+1010=1+102+103+...+109=102+103+....+109+1010
=(12+13+14+....+110)×10=(12+13+14+....+110)×10 (1)
Từ (1), suy ra:
(12+13+14+...+110)×x=(12+13+14+....+110)×10(12+13+14+...+110)×x=(12+13+14+....+110)×10
⇒x=10⇒x=10
Vậy x=10x=10
~ Học tốt ~
29 tháng 8 2018
Ta có : (12+13+14+....+110)×x=19+28+....+82+91(12+13+14+....+110)×x=19+28+....+82+91
Đặt A=19+28+....+82+91A=19+28+....+82+91
=(9−1−1−....−1)+(82+1)+(73+1)+.....+(19+1)=(9−1−1−....−1)+(82+1)+(73+1)+.....+(19+1)
=1+102+103+...+109=102+103+....+109+1010=1+102+103+...+109=102+103+....+109+1010
=(12+13+14+....+110)×10=(12+13+14+....+110)×10 (1)
Từ (1), suy ra:
(12+13+14+...+110)×x=(12+13+14+....+110)×10(12+13+14+...+110)×x=(12+13+14+....+110)×10
⇒x=10⇒x=10
Vậy x=10x=10
~ Học tốt ~
CX
1
23 tháng 4 2019
b, \(x\)x \(\frac{1}{4}\)+ \(x\)x \(\frac{1}{5}\)+ \(x\)x 2 = 19,6
\(x\)x (\(\frac{1}{4}+\frac{1}{5}+2\)) = 19,6
\(x\)x\(\frac{49}{20}\)= 19,6
\(x\) = \(19,6:\frac{49}{20}\)
\(x=8\)
EK
1
11 tháng 10 2021
\(A=0,5-\left|x-3,5\right|\le0,5\\ A_{max}=0,5\Leftrightarrow x-3,5=0\Leftrightarrow x=3,5\\ B=-\left|1,4-x\right|2=-2\left|1,4-x\right|\le0\\ B_{min}=0\Leftrightarrow1,4-x=0\Leftrightarrow x=1,4\)
NL
2
30 tháng 4 2019
x/1.4+x/4.7+x/7.10+x/10.13+x/13.16=5/2
=>x/3(1/4-1/7+1/7-1/10+1/10-1/13+1/13-1/16)=5/2
=>x/3.(1/4-1/16)=5/2
=>x/3.3/16=5/2
=>x/3=5/2:3/16
=>x/3=40/3
=>x=40
Vậy x=40
30 tháng 4 2019
x/1.4 + x/4.7 + x/7.10 + x/10.13 + x/13.16 = 5/6
=> x.1/3.(3/1.4 + 3/4.7 + 3/7.10 + 3/10.13 + 3/13.16) = 5/6
=> x.1/3.(1 - 1/4 + 1/4 - 1/7 + 1/7 - 1/10 + 1/10 - 1/13 + 1/13 - 1/16) = 5/6
=> x.1/3.(1 - 1/16) = 5/6
=> x.1/3.15/16 = 5/6
=> x.1/3 = 5/6 : 15/16
=> x.1/3 = 8/9
=> x = 8/9 : 1/3
=> x = 8/3
\(\Leftrightarrow2^x+16=16\Leftrightarrow2^x=0\\ \)
=> Không có giá trị nào của x để 2^x =0
Vậy pt vô nghiệm
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