SOLUTION: Plz help me to explain the range of this equation...{x^2-2x-3=0}

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Question 1000272: Plz help me to explain the range of this equation...{x^2-2x-3=0}
Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!

As with any function, the domain of a quadratic function f(x) is the set of x-values for which the function is defined, and the range is the set of all the output values (values of f).
Quadratic functions generally have the whole real line as their domain:
any x is a legitimate input.
The range is restricted to those points greater than or equal to the y-coordinate of the vertex (or less than or equal to, depending on whether the parabola opens up or down).
you are given x%5E2-2x-3=0 ...since coefficient a=1 which is positive number, your parabola opens up
The equation for a parabola can also be written in "vertex form":
y+=+a%28x+-+h%29%5E2+%2B+k
y=x%5E2-2x-3
y=%28x%5E2-2x%2Bb%5E2%29-b%5E2-3
y=%28x%5E2-2x%2B1%5E2%29-1%5E2-3
y=%28x-1%29%5E2-1-3
y=%28x-1%29%5E2-4
=>h=1 and k=-4
the vertex of your parabola is at (1,-4)
so, the range will be all values of y from -4 to infinity
or { y element of R: y%3E=-4 }
in interval notation:
[-4,infinity)

+graph%28+600%2C+600%2C+-10%2C+10%2C+-10%2C+10%2C+%28x-1%29%5E2-4%29+