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LoginA math - modulus functions
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Find the value of a and b for which 4 - 2x^2 + 8x can be expressed in the form a - 2(x-b)^2. Hence sketch the curve y = |4-2x^2+8x| for the interval -1< or equal to x < or equal to 5, indicating exact values of x-intercepts.
No problem finding a and b. Just wanna inquire about the graph plotting part. since this is a quadratic graph, do you go about getting the points using this method.
When y=0, x=_____(do working)
when x=0, y = ______
Find the coordinates turning points.
Find coordinates of end points.
or do you do so using table plotting?
Edited by bonkysleuth 06 Jul `08, 1:25PM
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you plot without the modulus sign first
then you reflect the -ve portion about the x-axis, and change it to positive
Reasoning: -1 becomes 1, and -2 becomes 2
so if the original turning point was at (x, -2), after modulus, it will become (x, 2)In short, just reflect everything under the x-axis to above the x-axis, and keep everything above the x-axis the same
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Originally posted by eagle:
you plot without the modulus sign first
then you reflect the -ve portion about the x-axis, and change it to positive
Reasoning: -1 becomes 1, and -2 becomes 2
so if the original turning point was at (x, -2), after modulus, it will become (x, 2)In short, just reflect everything under the x-axis to above the x-axis, and keep everything above the x-axis the same
Eh, as in for the points used, do i do all the values ranging from -1 to 5??? or i can skip a few of the values? this is the table plotting style... otherwise, i have to use the when y=0, x=___, format.
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Originally posted by bonkysleuth:
Eh, as in for the points used, do i do all the values ranging from -1 to 5??? or i can skip a few of the values? this is the table plotting style... otherwise, i have to use the when y=0, x=___, format.since it is a sketch, the things you need to take note are usually, as what jiaxing has mentioned, the x and y intercepts, and the stationary points (turning points and points of inflexion).
In more advanced F maths (in the past), you will need to find the equations of asymptotes, and how the curve will behave as x tends to +ve or -ve infinity.
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