Domain & Range of Inverse: Find g^-1(x) if g(x)=8X - x^2 ( for x larger than and equal to4).

[bluemitmit]

like the story!

[TheUltraDude]

I thought that the range of the function was the domain of the inverse.

I thought the range is found by simply subbing x=4 into the function, making the range of the inverse x>=16.

Why is this not so?

[TucsonMathDoc]

@TheUltraDude

you're almost there. It's true that "range of the function was the domain of the inverse", so the result ought be the same as the video's answer. This is because the range of g(x), given x>=4, is g(x)<=16 since the function is a parabola facing DOWN, not UP. Thanks for commenting.

[TheUltraDude]

@TucsonMathDoc oooh, I get it. Thanks a bunch.

I left a comment on your channel about asking you a couple more questions.

How would you like me to send them to you?

[TucsonMathDoc]

@TheUltraDude

Thank you for commenting. Glad you find it helpful.

I don't usually answer specific questions unless they're general enough that others can benefit.

Cheers,

MathDoc

[TheUltraDude]

Many thanks!

I never remember to start by completing the square!