Here might be a slightly easier approach
log7 (x) + log7 (x + 6) = 1
Note that we can write 1 as log7(7)
And using a log property, we can write the left side as log7 [ x * (x + 6)] ....so we have
log7 (x * (x + 6) ] = log7(7) and we can get rid of the logs and solve this equation :
x * (x + 6) = 7
x^2 + 6x = 7
x^2 +6x - 7 = 0 factor
(x + 7) (x - 1) = 0 and setting both factors to 0, we have that x = 1, or x = -7
We must reject the second solution because it requires taking the logs of negative numbers in the original equation, and this is not defined........so, the aswer is ..... x = 1
Solve for X:
(log(X))/(log(7))+(log(X+6))/(log(7)) = 1
Rewrite the left hand side by combining fractions. (log(X))/(log(7))+(log(X+6))/(log(7)) = (log(X)+log(X+6))/(log(7)):
(log(X)+log(X+6))/(log(7)) = 1
Multiply both sides by log(7):
log(X)+log(X+6) = log(7)
log(X)+log(X+6) = log(X (X+6)):
log(X (X+6)) = log(7)
Cancel logarithms by taking exp of both sides:
X (X+6) = 7
Expand out terms of the left hand side:
X^2+6 X = 7
Add 9 to both sides:
X^2+6 X+9 = 16
Write the left hand side as a square:
(X+3)^2 = 16
Take the square root of both sides:
X+3 = 4 or X+3 = -4
Subtract 3 from both sides:
X = 1 or X+3 = -4
Subtract 3 from both sides:
X = 1 or X = -7
(log(X))/(log(7))+(log(X+6))/(log(7)) => (log(-7))/(log(7))+(log(6-7))/(log(7)) = 1+((2 i) pi)/(log(7)) ~~ 1.+3.22892 i:
So this solution is incorrect
(log(X))/(log(7))+(log(X+6))/(log(7)) => (log(1))/(log(7))+(log(6+1))/(log(7)) = 1:
So this solution is correct
The solution is:
Answer: |
| X = 1
Here might be a slightly easier approach
log7 (x) + log7 (x + 6) = 1
Note that we can write 1 as log7(7)
And using a log property, we can write the left side as log7 [ x * (x + 6)] ....so we have
log7 (x * (x + 6) ] = log7(7) and we can get rid of the logs and solve this equation :
x * (x + 6) = 7
x^2 + 6x = 7
x^2 +6x - 7 = 0 factor
(x + 7) (x - 1) = 0 and setting both factors to 0, we have that x = 1, or x = -7
We must reject the second solution because it requires taking the logs of negative numbers in the original equation, and this is not defined........so, the aswer is ..... x = 1