Solve the equation using square roots 2x^2=42

Solve the system of equations. y= 2x y= x^2 - 15

Can somebody 1. what is the formula for finding the vertical distance between two points on a coordinate plane?

Look at the figure below: triangle abc is a right triangle with angle abc equal to 90 degrees. the length of ac is 5 units and the length of ab is 4 units. d is a point above c. triangle adc is a right triangle with angle dac equal to 90 degrees and dc parallel to ab. what is the length, in units, of segment cd?