To solve this problem, we'll follow the steps outlined:
- Step 1: Recognize that the expression xln7 can be thought of in terms of the power property of logarithms, which helps reframe it into a single logarithm.
- Step 2: Apply the formula ln(ab)=blna. This tells us that if we have something of the form blna, we can express it as ln(ab).
- Step 3: Utilize the known expression and rule by substituting a=7 and b=x. Thus, xln7 becomes ln(7x).
Therefore, the rewritten expression for xln7 using logarithm rules is ln7x.
This matches choice 4 from the provided options.