If f(4)=0 then where is an x intercept and what is a factor? Please give a step by step if possible

Where m is the slope of the line and b is the y-intercept of the line, or the y-coordinate of the point at which the line crosses the y-axis. to write an equation in slope-intercept form, given a graph of that equation, pick two points on the line and use them to find the slope. this is the value of m in the equation.

First subtract 10 from both side
y^2+6y-16=0
(y+8)(y-2)=0
-8 and 2