9.2x10^-8
Move the decimal to the right 8 times. Since it is moved to the right, the exponent is negative.
All you need to do for this is 155-75 which would be 80 :) hope this helps
Again, a spreadsheet or suitable calculator makes this short work.
The sum is 184.
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The terms being summed are ...
2·3² +3 = 2·9 +3 = 18 +3 = 21
2·4² +3 = 35
2·5² +3 = 53
2·6² +3 = 75
Their total is
21 +35 +53 +75 = 184