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1) 2⁴.x - 3.5x = 5² - 2⁴
16x - 15x = 25 - 16
x = 9
2) 3².x + 2²x = 26.2² - 13
9x + 4x = 26.4 - 13
13x = 104 - 13
13x = 91
x = 91 : 13
x = 7
5) 6²x - 5²x = 11.2 - 11
36x - 25x = 22 - 11
11x = 11
x = 11 : 11
x = 1
3) 5²x - 2⁴x = 3⁴ - 16.3²
25x - 16x = 81 - 16.9
9x = -63
x = -63 : 9
x = -7
6) 7²x - 6²x = 13.2³ - 26
49x - 36x = 13.8 - 26
13x = 104 - 26
13x = 78
x = 78 : 13
x = 6
4) 7²x - 14x = 7².10 - 70
49x - 14x = 49.10 - 70
35x = 490 - 70
35x = 420
x = 420 : 35
x = 12
a)
\(\dfrac{6}{13}\cdot\dfrac{8}{7}\cdot\dfrac{-26}{3}\cdot\dfrac{-7}{8}\)
\(=\dfrac{6}{13}\cdot\dfrac{-26}{3}\cdot\dfrac{8}{7}\cdot\dfrac{-7}{8}\)
\(=-4\cdot\left(-1\right)\\ =4\)
b)
\(\dfrac{6}{11}+\dfrac{11}{3}\cdot\dfrac{3}{22}\)
\(=\dfrac{6}{11}+\dfrac{1}{2}\\ =\dfrac{12}{22}+\dfrac{11}{22}\\ =\dfrac{23}{22}\)
Bài 6:
\(21,251+6,058+0,749+1,042\)
\(=\left(21,251+0,749\right)+\left(6,058+1,042\right)\)
\(=22+7,1\)
\(=29,1\)
___________________
\(1,53+5,309+12,47+5,691\)
\(=\left(1,53+12,47\right)+\left(5,309+5,691\right)\)
\(=14+11\)
\(=25\)
5:
a: =>x/17=5/17
=>x=5
b; =>6+x=7/11*33=21
=>x=15
c: \(\dfrac{12+x}{43-x}=\dfrac{2}{3}\)
=>3x+36=86-2x
=>5x=50
=>x=10
d: \(\dfrac{x}{5}< \dfrac{3}{7}\)
=>x<3/7*5
=>x<15/7
f: 15/26+x/16=46/52
=>x/16=23/26-15/26=8/26=4/13
=>x=4/13*16=64/13
6(x+11) - 7(2-x) = 26
\(\Rightarrow\)6x + 66 - 14 +7x = 26
\(\Rightarrow\)13x + 52 = 26
\(\Rightarrow\)13x = -26
\(\Rightarrow\)x = -2
f) 11.(x+2)=5.x+40
=> 11x+22=5x+40
=> 6x=18
=> x=18:6=3
g)11.(x-6)=4.x+11
=> 11.x+(-66)=4x+11
=> 7x=77
=> x=77:7=11
h) (3x-4):x+10=12
=> 3x:x-4:x=12-10=2
=> 3-4:x=2
=> 4:x=3-2=1
=> x=4:1=4
k)(5x+7):x+20=26
=> 5x:x+7:x=26-20=6
=> 5+7:x=6
=> => 7:x=6-5=1
=> x=7:1=7
m) x.1999-x=1999.1997+1999
=> x.1998=1999.(1997+1)
=> x.1998=1999.1998
=> x=1999
**** cho mik nha Nguyễn Thị Thảo Ly
Thiếu kết luận là bay mất 0.25 điểm rồi:)
\(6\left(x+11\right)-7\left(2-x\right)=26\)
\(\Rightarrow6x+66-14+7x=26\)
\(\Rightarrow13x+52=26\)
\(\Rightarrow13x=26-52\)
\(\Rightarrow13x=-26\)
\(\Rightarrow x=-26:13\)
\(\Rightarrow x=-2\)