For f(x)= 1-x-x^2, a=0 find tangent slope of tangent line? find slope of tangent line mtan=f'(a), and find the equation of the tangent line to f at x=a

Scores on a university exam are normally distributed with a mean of 78 and a standard deviation of 8. the professor teaching the class declares that a score of 70 or higher is required for a grade of at least “c.” using the 68-95-99.7 rule, what percentage of students failed to earn a grade of at least “c”?