Thursday, February 16, 2012

What are x and y intercepts of the graph of f(x) = x^2 - 3x + 2 .

The y-intercept of the graph is the point where
the function crosses the y-axis.  The x-value is equal to zero for every point on the
y-axis.


1. Substitute x = 0 into the given function: y =
(0)^2 - 3(0) + 2 = 0 - 0 + 2 = 2.  Therefore the y-intercept is at the point (0,
2).


The x-intercept of the graph is the point where the
function crosses teh x-axis.  The y-value is equal to zero for every point on the
x-axis.


2. Substitute y = 0 into the given function: 0 =
x^2 - 3x + 2. 


Since this is a quadratic function we can
factor the equation or use the quadratic formula.


3. 0 =
x^2 - 3x + 2          (Need to find the factors of 2 whose sum is equal to -3).  (-2) x
(-1) = 2 and (-2) + (-1) = -3, so:


0 = (x - 2) (x -
1)


0 = x - 2     and     0 = x - 1          Solve both
equations for x.


+ 2    + 2             + 1     
+1


2 = x     and     1 = x


The
x-intercepts are at 1 and 2, so the coordinates are (1, 0) and (2,
0).

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