Simplify each expression by combining like terms.
4a+8b
Please explain if you can

Ineed asap.i cant understand this question i need someone to me right away

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.

Find the slope of the line that contains the following points. r(-2, 4), s(6, -2)