The denominator can be factored as:
2x2+4x−6=2(x+3)(x−1)
The function is undefined at x=1 and x=−3.
Let y=f(x) and cross-multiply:
y(2x2+4x−6)=2x−3
2yx2+(4y−2)x+(3−6y)=0
For x to be real, the discriminant of this quadratic must be ≥0.
When y=0, the equation becomes:
−2x+3=0
x=23
This is a valid x-value (not excluded from the domain), so y=0 is in the range.
When y=0, applying the discriminant condition Δ≥0:
Δ=(4y−2)2−4(2y)(3−6y)≥0
=16y2−16y+4−24y+48y2≥0
=64y2−40y+4≥0
=4(16y2−10y+1)≥0
16y2−10y+1≥0
Roots of 16y2−10y+1=0:
y=3210±100−64
=3210±6
y=81 or y=21
Since the coefficient of y2 is positive, the parabola opens upward, so the expression is ≥0 outside the roots:
y≤81 or y≥21
Checking whether the excluded points x=1 and x=−3 affect the range:
Substituting x=1 into 2yx2+(4y−2)x+(3−6y)=0 gives 1=0.
Substituting x=−3 gives 9=0.
Neither excluded point is ever a solution, so no y-values need to be removed.
Range of f(x)=(−∞,81]∪[21,∞)
The correct answer is Option 2.