Can anyone solve this using the "completing the square" method? (or something similar) Solve for X

Describe the 2 algebraic methods you can use to find the zeros of the function f(t)=-16t^2+400.

Complete the solution of the equation. find the value of y when x equals to 28 x+3y=28

The area (a) of a circle with a radius of r is given by the formula and its diameter (d) is given by d=2r. arrange the equations in the correct sequence to rewrite the formula for diameter in terms of the area of the circle.