Factorise: 30x^5+15x²y²+xy​

Evaluate the expression for the given value of the variable 2×(c2-5) for c=4

If y varies directly as x2 and y=6 when x=6, find the constant of variation.

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”?