How do u find the range of a graph? A quadratic one?

Question

cwrw238 · Answer

example 
find range of f(x)  =  x^2 - 5x + 4
the graph will look like a U so will have a minimum  value 
you can plot the graph  to find the range or you can convert the function to vertex form
by completing the square

x^2 - 5x + 4 = (x - 2.5)^2 - 2.5^2 + 4
-  the x coordinate of the vertex is 2.5
and y =  (2.5)^2 - 5(2.5) + 4 =  6.25 - 12.5 + 4 =  -2.25
this is minimum value of f(x)

so the range is [-2.25, infinity)

functions having a negative x^2 have upside down U shape so have a maximum value

anonymous · Answer

OMG, thx so much!!
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