to Sir Jagoll (and of course everybody else)
(1)
y=((x^2 −x−6)/(x^2 −3x−4))=
=(((x−3)(x+2))/((x−4)(x+1))) ⇒
⇒ { ((zeros at x=−2; x=3)),((vertical asymptotes at x=−1; x=4)) :}
defined for x∈R\{−1; 4}
range: transforming y=((x^2 −x−6)/(x^2 −3x−4)) to
x^2 −((3y−1)/(y−1))x−((2(2y−3))/(y−1))=0
D=((25y^2 −46y+25)/(4(y−1)^2 ))>0∀x∈R ⇒
⇒ { ((range=R)),((horizontal asymptote at y=1 (∗))) :}
(∗) doesn′t mean y=1 is not within range!!!
x=1 ⇒ y=1
y′=−((2(x^2 −2x+7))/((x−4)^2 (x+1)^2 )) no real zeros ⇒
⇒ no local extremes
y′′=((4(x^3 −3x^2 +21x−25))/((x−4)^3 (x+1)^3 ))=0 at x≈1.33131 ⇒
⇒ turning point
(2)
y=((x^2 −x−6)/(x^2 −3x+4))=
=(((x−3)(x+2))/(x^2 −3x+4)); x^2 −3x+4=0 no real zeros ⇒
⇒ { ((zeros at x=−2; x=3)),((no vertical asymptote)) :}
defined for x∈R
range: transforming y=((x^2 −x−6)/(x^2 −3x+4)) to
x^2 −((3y−1)/(y−1))x+((2(2y+3))/(y−1))=0
D=−((7y^2 +14y−25)/(4(y−1)^2 ))≥0 for −1−((4(√(14)))/7)≤y≤−1+((4(√(14)))/7) ⇒
⇒ { ((range=[−1−((4(√(14)))/7); −1+((4(√(14)))/7)])),((horizontal asymptote at y=1 (∗))) :}
(∗) doesn′t mean y=1 is not within range!!!
x=5 ⇒ y=1
y′=−((2(x^2 −10x+11))/((x^2 −3x+4)^2 ))=0 at x=5±(√(14))
y^(′′) =((4(x^3 −15x^2 +33x−13))/((x^2 −3x+4)^3 ))
y′′ { ((>0 at x=5−(√(14)) ⇒ local minimum)),((<0 at x=5+(√(14)) ⇒ local maximum)),((=0 at { ((x≈.506699)),((x≈2.06421)),((x≈12.4291)) :} ⇒ 3 turning points )) :}
(3)
y=((x^2 −x+6)/(x^2 −3x−4))=
=((x^2 −x+6)/((x−4)(x+1))) ⇒
⇒ { ((no real zeros)),((vertical asymptotes at x=−1; x=4)) :}
defined for x∈R\{−1; 4}
range: transforming y=((x^2 −x+6)/(x^2 −3x−4)) to
x^2 −((3y−1)/(y−1))x−((2(2y+3))/(y−1))=0
D=((25y^2 +2y−23)/(4(y−1)^2 ))<0 for −1<y<((23)/(25)) ⇒
⇒ { ((range=R\]−1; ((23)/(25))[)),((horizontal asymptote at y=1 (∗))) :}
(∗) doesn′t mean y=1 is not within range!!!
x=−5 ⇒ y=1
y′=−((2(x^2 +10x−11))/((x−4)^2 (x+1)^2 ))=0 at x=−11; x=1
y′′=((4(x^3 +15x^2 −33x+53))/((x−4)^3 (x+1)^3 ))
y′′ { ((>0 at x=−11 ⇒ local minimum)),((<0 at x=1 ⇒ local maximum)),((=0 at x≈−17.1098 ⇒ turning point)) :}
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