\(4^{3x+1}-8.4^2=8.4^2\)

\(\Rightarrow4^{3x}.4=8.4^2+8.4^2=16.4^2\)

\(\Rightarrow4^{3^x}=4.4.4=4^3\)

\(\Rightarrow3x=3\)

\(\Rightarrow x=1\)

\(7^{5x-1}=7^4\)

\(\Rightarrow5x-1=4\)

\(\Rightarrow5x=5\)

\(\Rightarrow x=1\)

Các bạn ơi,mình ghi thiếu,còn 3 câu nữa nha!!!~~nya

e)| \(\dfrac{5}{2}\)x-\(\dfrac{1}{2}\) |-(-2²).\(\dfrac{1}{3}\)(0,75-\(\dfrac{1}{7}\))=\(\dfrac{-5}{13}\):2\(\dfrac{9}{13}\)-0,5.(\(\dfrac{-2}{3}\))

f)| 5x+21 | = | 2x -63 |

g) -45 - |-3x-96 | - 54=-207

Làm ơn giúp mình với ạ!Mình đang cần gấp lắm trong ngày hôm nay ạ!!!Mình xin cảm ơn các bạn nhiều nhiều lắm luôn đó!!!Thank you very much!!!(^-^)

a, (\(\dfrac{2}{9}\)(6x - \(\dfrac{3}{4}\)) - 3(\(\dfrac{1}{4}x-\dfrac{1}{5}\)) = \(\dfrac{-8}{15}\)

<=> (\(\dfrac{4}{3}x-\dfrac{1}{6}\)) - (\(\dfrac{3}{4}x-\dfrac{3}{5}\)) = \(\dfrac{-8}{15}\)

<=> \(\dfrac{4}{3}x-\dfrac{1}{6}-\dfrac{3}{4}x+\dfrac{3}{5}=\dfrac{-8}{15}\)

<=> \(\dfrac{7}{12}x+\dfrac{13}{30}=\dfrac{-8}{15}\)

<=> \(\dfrac{7}{12}x=\dfrac{-8}{15}-\dfrac{13}{30}\)

<=> \(\dfrac{7}{12}x=-\dfrac{29}{30}\)

<=> x = \(-\dfrac{58}{35}\)
@Nguyễn Gia Hân

dễ vct \(\frac{3}{1^2.2^2}=\frac{1}{1^2}-\frac{1}{2^2}\)

tương tự

a với e chi ở đây

\(A=\frac{3}{1^2.2^2}+\frac{5}{2^2.3^2}+...+\frac{19}{9^2.10^2}\)

\(A=\frac{3}{1.4}+\frac{5}{4.9}+...+\frac{19}{81.100}\)

\(A=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{9}+...+\frac{1}{81}-\frac{1}{100}\)

\(A=1-\frac{1}{100}\)

\(A=\frac{99}{100}\)

Chúc bạn học tốt+-*/

sau \(\frac{19}{9^2.10^2}\) là so sánh A với 1

b) \(\frac{3}{x-5}=\frac{-4}{x+2}\)

=> 3.(x + 2) = (x - 5). (-4)

= 3x + 6 = -4x + 20

= 3x - 4x = 26

=> -x = 26

=> x = -26

c) \(\frac{x}{-2}=\frac{-8}{x}\)

=> x.x = -2 . (-8)

 => x² = 16

=> x = 4

t i c k nha!!! 645646677778879078452352543546456457567564546567

còn câu a

b: =>3|x-5|=8+4=12

=>|x-5|=4

=>x-5=4 hoặc x-5=-4

=>x=9 hoặc x=1

d: =>2x+6=3-3x-2

=>2x+6=1-3x

=>5x=-5

hay x=-1

e: \(\Leftrightarrow x-3\inƯC\left(70;98\right)\)

\(\Leftrightarrow x-3\in\left\{1;2;7;14\right\}\)

mà x>8

nên \(x\in\left\{10;17\right\}\)

72-x nhân9 -   x -70 nhân7

= 648 - 9x - 7x-490 

=158-2x

Ta có \(\frac{72-x}{7}-\frac{x-70}{9}=\frac{\left(72-x\right).9}{7.9}-\frac{\left(x-70\right).7}{9.7}=\frac{648-9x}{63}-\frac{7x-490}{63}\)

\(=\frac{648-9x-7x-490}{63}=\frac{158-2x}{63}\)

a: Ta có: \(x\in B\left(15\right)\)

nên \(x\in\left\{0;15;30;45;60;75;...\right\}\)

mà 40<=x<=70

nên \(x\in\left\{45;60\right\}\)

b: \(2011^2\cdot2011^x=2011^7\)

\(\Leftrightarrow x+2=7\)

hay x=5