What is the geometric mean between 4 and 9?

When using the linear combination metho e linear combination method to solve a system of linear equations, the four options are:

The chs baseball team was on the field and the batter popped the ball up. the equation b(t)=80t-16•16+3.5 represents the height of the ball above the ground in feet as a function of time in seconds. how long will the catcher have to get in position to catch the ball before it hits the ground? round to the nearest second

Are triangles the congruent? write the congruency statement.what is the congruency that proves they are congruent? what is the perimeter of ∆pqr?