4z = 2(z + 4)
Please help me solve this

To solve the system of equations below, pedro isolated the variable y in the first equation and then substituted it into the second equation. what was the resulting equation? { 5y=10x {x^2+y^2=36

The distance of a chord from the centre of a circle is 12cm and the lenght of the chord is 10cm. find the radius of the circle

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