Solve the following equations ln x ln 3 lnx 2 logx 3 1
Solve the following equations. ln x = ln 3 - ln(x - 2). log(x + 3) = 1 - log(x - 2). log(x - 1) = log(2/x) + log(3x - 5).
Solution
1) 4^(2x +3) =16.2^(x-2)
RHS 16.2^(x-2) = 2^4^(x-2) = 2^(x+2)
LHS 4^(2x +3) =2^2(2x +3) = 2^(4x+6)
2^(x+2) = 2^(4x+6)
when bases are same we can equate the exponents:
4x +6 = x+2
3x = 4
x = 4/3
2) lnx = ln3 - ln(x -2)
use the property : lnA - lnB = lnA/B
RHS : ln3 - ln(x -2) = ln(3/x-2)
lnx = ln(3/(x-2) )
equate the argument inside the log:
x = 3/(x -2)
x(x-2) =3
x^2 -2x -3 =0
factorise : x^2 -3x +x -3 =0
x(x -3) +1(x-3) =0
(x +1)(x -3) =0
x = -1 , 3
3) log(x +3) = 1- log(x -2)
log(x +3) +log(x -2) = 1
log[(x +3)(x-2)] =1
(x+3)(x-2) = 10^1
x^2 +x -6 =10
x^2 + x -16 =0
Roots of quadratic equation cab be found using quadratic formula:
x = (-b +/- sqrt(b^2 -4ac) )/2a
= ( -1 +/ sqrt(65)/2
= -1/2 +/- sqrt(65)/2
