Answer:
<h3>He should have found 8 as the exponent, not –8.</h3>
Step-by-step explanation:
Given the expression simplified by Pablo as 
On simplification we have;
According to one of the law of indices 
Applying this law to the question will give;

Based on the calculation above, the exponent of 2 is 8 which means that Pablo should have found 8 as the exponent, not –8.
The appropriate formula here is l = a + (n-1)d, where l represents the last term.
Here the first term is -5 and the common difference is +4. Thus,
l = -5 + (n-1)(4) (answer)
Check: we are given the arith sequence -5, -1, 3, 7. Does our formula correctly predict the 1st term? l = -5 + (1-1)(4) = > -5. Yes.
Does it correctly predict the 3rd term? l = -5 +(3-1)(4) => -5+2(4) = 3. Yes