63n^2 - 126n = -56 solve by factoring

Which of the following is correct interpretation of the expression -4+13

He weights of 2-pound bags of best dog food are approximately normally distributed with a given mean  and standard deviation  according to the empirical rule, what percentage of the bags will have weights within 3 standard deviations of the mean? 47.5%68%95%99.7%

Aquadratic equation in standard from is written ax^2= bx+c, where a,b and c are real numbers and a is not zero?