The electric cooperative needs to know the mean household usage of electricity by its non-commercial customers in kWh per day. They would like the estimate to have a maximum error of 0.09 kWh. A previous study found that for an average family the standard deviation is 1.9 kWh and the mean is 19.9 kWh per day. If they are using a 80% level of confidence, how large of a sample is required to estimate the mean usage of electricity? Round your answer up to the next integer.

1. The area of a rectangular barnyard is given by the trinomial 4x ^ 2 + 4x-3. What are the possible dimensions of the barnyard? Use factoring
 4x ^ 2 + 4x-3
 For this case, the first thing we must do is factorize the given expression.
 We have then factoring:
 (2x-1) * (2x + 3)
 Therefore the dimensions of the rectangle are:
 (2x-1)
 (2x + 3)
 
 the possible dimensions of the barnyard are:
 (2x-1)
 (2x + 3)
 2. The area of a rectangular picture frame is given by the trinomial 6x ^ 2-11x-72. What are the possible dimensions of the frame? Use factoring
 6x ^ 2-11x-72
 For this case, the first thing we must do is factorize the given expression.
 We have then factoring:
 (3x + 8) * (2x-9)
 Therefore the dimensions of the rectangle are:
 (3x + 8)
 (2x-9)
 
 the possible dimensions of the frame are:
 (3x + 8)
 (2x-9)