Question

Tìm x:

 

a) 2². 14^x. 7² =14¹⁰⁰

b) 15. x + 3 .(x+2) =96

 

c) 2^x + 4.2^x =5.2⁵

 

Giúp mình với. Cảm ơn các bạn nhiều nhiều^^

 

Answer 1

a) 2².14^x . 7² = 14¹⁰⁰

=> (2.7)² . 14^x = 14¹⁰⁰

=> 14^x = 14¹⁰⁰ : 14²

=> 14^x = 14⁹⁸

=> x = 98

b) 15.x + 3(x + 2) = 96

=> 15x + 3x + 6 = 96

=> 18x = 96 - 6

=> 18x = 90

=> x = 90 : 18 = 5

c) 2^x + 4.2^x = 5.2⁵

=> 2^x(1 + 4) = 5.2⁵

=> 2^x .5= 5.2⁵

=> 2^x = 5.2⁵ : 5

=> 2^x = 2⁵

=> x = 5

Answer 2

\(a,2^2.14^x.7^2=14^{100}\)

\(\Rightarrow14^2.14^x=14^{100}\)

\(\Rightarrow14^x=14^{98}\)

\(\Rightarrow x=98\)

\(b,15.x+3\left(x+2\right)=96\)

\(\Rightarrow3\left(5x+x+2\right)=96\)

\(\Rightarrow6x+2=32\)

\(\Rightarrow6x=30\)

\(\Rightarrow x=5\)

\(c,2^x+4.2^x=5.2^5\)

\(\Rightarrow2^x\left(1+4\right)=5.2^5\)

\(\Rightarrow2^x.5=5.2^5\)

\(\Rightarrow2^x=2^5\)

\(\Rightarrow x=5\)