1. Finding x- and y-intercepts algebraically

2. y-intercepts
For every point along the y-axis, the value of x will be zero (x=0)
We can use this fact to find y-intercepts if we have an equation for a function.
EXAMPLE: If y = 2x – 3 and we know that x = 0…
we can plug in zero for x and simplify to find y: y = 2(0) – 3
y = 0 – 3
y = -3
This means that if we were to graph f(x) = 2x – 3, as you can see on the next slide, the graph would cross the y-axis at the point (0, -13) where x = 0 and y = -13

3. Graph of f(x) = y = 2x – 3

4. x-intercepts
For every point along the x-axis, the value of y will be zero (x=0)
We can use this fact to find x-intercepts if we have an equation for a function.
EXAMPLE: If y = -½x2 + 8 and we know that y = 0…
we can plug in zero for y and solve to find x:
0 = -½x x2 = 16
-8 = -½x2 x = ±4
(-8)÷(-½) = x2
This means that if we were to graph f(x) = -½x2 + 8, as you can see on the next slide, the graph would cross the x-axis at (-4, 0) and (4, 0).

5. Graph of f(x) = y = -½x2 + 8