Respuesta :
Given:
[tex]e^{4x}-e^{2x}=12[/tex]To Determine: The value of x
Solution
[tex]\begin{gathered} e^{4x}-e^{2x}=12 \\ (e^x)^4-(e^x)^2=12 \end{gathered}[/tex][tex]\begin{gathered} let:a=e^x \\ Therefore, \\ (e^x)^4-(e^x)^2=12 \\ a^4-a^2=12 \\ a^4-a^2-12=0 \end{gathered}[/tex]Solve the derived equation by factorizing completing
[tex]\begin{gathered} a^4-a^2-12=0 \\ a^4-4a^2+3a^2-12=0 \\ a^2(a^2-4)+3(a^2-4)=0 \\ (a^2-4)(a^2+3)=0 \\ a^2-4=0,or,a^2+3=0 \end{gathered}[/tex][tex]\begin{gathered} a^2-4=0 \\ a^2-2^2=0 \\ diiference\text{ of two square is expanded as} \\ a^2-b^2=(a-b)(a+b) \\ Therefore \\ a^2-2^2=0 \\ (a-2)(a+2)=0 \\ a-2=0,or,a+2=0 \\ a=2,a=-2 \end{gathered}[/tex][tex]\begin{gathered} Also,a^2+3=0 \\ a^2=-3(No\text{ solution because square root of a negative number is an imaginary number\rparen} \end{gathered}[/tex]Therefore
[tex]a=2,or,a=-2[/tex][tex]\begin{gathered} e^x=a \\ e^x=2,or,e^x=-2(no\text{ solution\rparen} \\ x=ln2 \\ x=0.693 \end{gathered}[/tex]Hence, the value of x is 0.693
