How do you solve 4(7^(x + 2)) = 9^(2x - 3)4(7x+2)=92x3?

1 Answer
Apr 22, 2018

x=(-3ln(9)-2ln(7)-ln(4))/(ln(7)-2ln(9))x=3ln(9)2ln(7)ln(4)ln(7)2ln(9)

Explanation:

you have to log the equations

4*7^(x+2)=9^(2x-3)47x+2=92x3

Use either natural logs or normal logs lnln or loglog and log both sides

ln(4*7^(x+2))=ln(9^(2x-3))ln(47x+2)=ln(92x3)

First use the log rule that states loga*b=loga+logblogab=loga+logb

ln(4)+ln(7^(x+2))=ln(9^(2x-3))ln(4)+ln(7x+2)=ln(92x3)

Remember the log rule that states logx^4=4logxlogx4=4logx

ln(4)+(x+2)ln(7)=(2x-3)ln(9)ln(4)+(x+2)ln(7)=(2x3)ln(9)

ln(4)+xln(7)+2ln(7)=2xln(9)-3ln(9)ln(4)+xln(7)+2ln(7)=2xln(9)3ln(9)

Bring all the xlnxln terms to one side

xln(7)-2xln(9)=-3ln(9)-2ln(7)-ln(4)xln(7)2xln(9)=3ln(9)2ln(7)ln(4)

Factorise the x out

x(ln(7)-2ln(9))=(-3ln(9)-2ln(7)-ln(4))x(ln(7)2ln(9))=(3ln(9)2ln(7)ln(4))

x=(-3ln(9)-2ln(7)-ln(4))/(ln(7)-2ln(9))x=3ln(9)2ln(7)ln(4)ln(7)2ln(9)

Solve on the calculator using the ln button or if your calculator doesn't have it use the log base 10 button.