Define the parabola equation when the vertex is the same center point of a circle x^2+y^2+4x-6y-12=0 with y=8 is the diectrix of its. a)x^2-4x+20y-56=0 b)x^2+4x-20y+56=0 c)x^2+4x+20y-56=0 d)x^2+4x-20y-56=0

Arandom sample of 45 observations results in a sample mean of 68. the population standard deviation is known to be 23 a. compute the margin of error at a 959% confidence interval. b. compute the 95% confidence interval for the population mean c. compute the 90% confidence interval for the population mean. d. compute the 75% confidence interval for the population mean