Solve x^2+12x=-11by completing the square which is the solution set of the equation A={-11,-1} B={-11,1} C={11,-1} D={11,1}

1. according to the internal revenue service, the mean tax refund for the year 2007 was $2,708. assume the standard deviation is $650 and that the amounts refunded follow a normal probability distribution. a. what percent of the refunds are more than $3,000? b. what percent of the refunds are more than $3,000 but less than $4,000? c. what percent of the refunds are less than $2,000?