The gradient function of a cough is kx^2-mx, where k and m are constant. The curve has a turning point at (4,-5). The gradient of the tangent to the curve at the point x=-2 is 9​

Idon’t understand this.. will someone ? will mark brainliest along with 20 points.

Rockwell hardness of pins of a certain type is known to have a mean value of 50 and a standard deviation of 1.1. (round your answers to four decimal places.) (a) if the distribution is normal, what is the probability that the sample mean hardness for a random sample of 8 pins is at least 51?

The triangles in the diagram are congruent. if mzf = 40°, mza = 80°, and mzg = 60°, what is mzb?