What’s an equivalent expression of -1/2(-2x+4y) ?

The graph shows the distance y, in inches, a pendulum moves to the right (positive displacement) and to the left (negative displacement), for a given number of seconds x. how many seconds are required for the pendulum to move from its resting position and return? enter your answer in the box.

What is the number 321,000,000 in scientific notation? also what is the number? ?

The tile along the edge of a triangular community pool needs to be replaced? ?