√(-80) = √(4²×5(-1)) = 4√5 √(-1) = 4√5i.
Do you have any pictures to choose from anything to show what im looking at?
The first term, a, is 2. The common ratio, r, is 4. Thus,
a_(n+1) = 2(4)^(n).
Check: What's the first term? Let n=1. Then we get 2(4)^1, or 8. Is that correct? No.
Try this instead:
a_(n) = a_0*4^(n-1). Is this correct? Seeking the first term (n=1), does this formula produce 2? 2*4^0 = 2*1 = 2. YES.
The desired explicit formula is a_(n) = a_0*4^(n-1), where n begins at 1.
Since a product in maths means the result after multiplying numbers, you need to multiply 2 prime numbers and get 4.
If we look at the prime numbers: 2, 3, 5, 7, 11, etc, we see that the only number we can multiply to get 4 is 2, or, in other words, the only multiplication of prime numbers we can do to get four is 2*2=4.
