7^{x + 2} + 2.7^{x - 1} = 345

7^x . 7² + 2 . 7^x : 7 = 345

7^x . 49 + 2 . 7^x . \(\frac{1}{7}\)= 345

7^x . (49 + 2.\(\frac{1}{7}\)) = 345

7^x . \(\frac{345}{7}\)= 345

7^x = 345 . \(\frac{7}{345}\)

7^x = 7

=> x = 1 

tao chịu

mình giải ý c 

5(x+27)=200

(x+27)=200:5

(x+27)=40

x=40-27

x=13

a) \(\left(2x+1\right)^2=25\)

=> \(2x+1=5\)         và       \(2x+1=-5\)

=>  \(2x=5-1=4\) và     \(2x=-5-1=-6\)

=>  \(x=4:2=2\) và   \(x=-6:2=-3\)

b) \(\left(x-1\right)^3=-125\)

=> \(x-1=-5\Rightarrow x=-5+1=-4\)

c)  \(2^{x+2}-2^x=96\)

=> \(2^x\cdot2^2-2^x\cdot1=96\)

=> \(2^x\left(2^2-1\right)=96\)

=> \(2^x\cdot3=96\Rightarrow2^x=96:2=32\)

=> \(x=5\)

d) \(7^{x+2}+2\cdot7^{x-1}=345\)

=> \(7^x\cdot7^2+2\cdot7^x:7=345\)

=> \(7^x\cdot7^2+2\cdot7^x\cdot\frac{1}{7}=345\)

=> \(7^x\cdot\left(7^2+2\cdot\frac{1}{7}\right)=345\)

=> \(7^x\cdot\frac{345}{7}=345\)

=> \(7^x=345:\frac{345}{7}=7\)

=> \(x=1\)

\(\left(2x+1\right)^2=25\)

\(\left(2x+1\right)^2=5^2=\left(-5\right)^2\)

\(TH1:\left(2x+1\right)^2=5^2\)

\(2x+1=5\)

\(x=\left(5-1\right):2\)

\(x=4\)

\(TH2:\left(2x+1\right)^2=\left(-5\right)^2\)

\(2x+1=-5\)

\(x=\left[\left(-5\right)-1\right]:2\)

\(x=-3\)

Vậy x=2 hoặc x= -3

=1000:y=200

y=1000:200

y=5

y=5 sai chắc à mà đúng

1000-345+345:y=655+345:5

1000-345+345:y=724

345+345:y=1000-724

345:y=276-345

y=345-131

y=214

=> x = 2004 - 345 = 1659

2004 - x = 345 

        x    = 2004 - 345

        x     = 1659 

x = 1659

a, x=2;y=1.                  b, x=2;y=4

Lam cach nao de ra duoc ket qua nhu vay ha ban?

a) \(aaaa:x=a\Rightarrow aaaa:a=x\Rightarrow x=1111\)

b) \(x\times a=a0a0a0\Rightarrow x=a0a0a0:a\Rightarrow x=101010\)