The sum of two numbers is greater than either number ?

An equation of the line tangent to y=x^3+3x^2+2 at its point of inflection is

Which expression is equivalent to 8(k + m) − 15(2k + 5m)?

Offering 30 if a plus b plus c equals 68 and ab plus bc plus ca equals 1121, where a, b, and c are all prime numbers, find the value of abc. the answer is 1978 but i need an explanation on how to get that.