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Graphing Parabolas: Introduction
Parabolas are of quadratic form y= ax² + bx +c
If a is positive, then the parabola will open upward and has minimum point.
If a is negative, the parabola will open downward and has maximum point.
Problem:
Will the graph of parabola y = 4x² + 8x - 18 open upward or
downward?
Solution:
Step 1: The parabola has equation in the quadratic form y= ax² + bx +c
Step 2: Comparing y = 4x² + 8x - 18 with the equation y= ax² + bx +c,
Step 3: A = -5, b = 4 and c = -4
Step 4: If a is negative, the parabola will open downward and has maximum
Step 5: Answer: Downward
Practice problem
A.
B.
Will the graph of parabola y = 2x² + 8x + 2 open upward or downward?
for the graph y= -4x² - 3x - 1
What is the equation of the axis of symmetry?
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