Maths
posted by Anonymous
f:x > (4x²8x21)/(x²1)
(a) Analyse
(b) Sketch
I'm struggling on (a) so I can't do (b)
Here are my ideas/what I've got so far:
(a)Domain, x is a set of real numbers; x can not equal 1
Asymptotes x=1, y=?
I think you have to divide here but i can't figure it out with the x² on the bottom.
zeroes: when x=0, y=21
when y=0, x=?
0=4x²8X21 then??
extrema; differentiate eqn here...not sure how (maybe convert to another form?)
I think that is all for the analysis?
For any help, thanks in advance

Reiny
where to begin ? ....
f:x > (4x²8x21)/(x²1) corresponds to the equation
y = (4x²8x21)/(x²1)
for vertical asymptotes, set the denominator equal to zero
so x^2  1 = 0
(x+1)(x1) = 0
x = ± 1
so there are two vertical asymptotes
at x = 1 and x = 1
for horizontal asymptotes, let x > ∞
for very large values of x, the signigicant part of the equation is
y = 4x^2 / x^2 which approaches 4
so y = 4 is the horizontal axis
for xintercepts, let y = 0
so (4x²8x21)/(x²1) = 0
(4x²8x21)= 0
(2x+3)(2x7) = 0
x = 3/2 and x = 7/2 are the xintercepts
for y intercepts , let x = 0 in the equation
so y = (0021)/(01) = 21
so the yintercept is 21
Derivative: by quotient rule
dy/dx = [(x^21)(8x8)  2x(4x^28x21)]/(x^2  1)^2
expanding the top and setting this equal to zero gave me
8x^2 + 34x + 8 = 0
solve this using the quadratic formula to get the x's of the extrema,
sub those x's back in the origianl to get their y's.
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