Can anyone help my brother please it’s test

You are studying different function tools and begin working with this function y=-160-9(x) use the equation to answer the question y=-160-9(x) what is the y value when x equals -13? y=-160-9(x)

Circle a has a diameter of 7 inches, a circumference of 21.98 inches, and an area of 38.465 square inches. the diameter of circle b is 6 inches, the circumference is 18.84 inches, and the area is 28.26 square inches. part a: using the formula for circumference, solve for the value of pi for each circle. (4 points) part b: use the formula for area and solve for the value of pi for each circle. (4 points)

What is the point of inflection for the function f(x)=2cos4x on the interval (0, pi/2)