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domain and range alevel maths

ls714

can someone explain to me how do you find the domain and the range from an equation??

Reply 1

booklover1313

Original post by lev0701

can someone explain to me how do you find the domain and the range from an equation??

Have you got an example?
Sometimes you can complete the square to find the minimum value.
Sometimes, if it is a fraction, you can find what the smallest denominator & largest numerator will be, and therefore the maximum.

Reply 2

ls714

Original post by booklover1313

i got this question where f(x)=square root of 1-9x^2 -a<x<a
and i had to find the range to it
the first question was also to find a and i got a=1, and that should be the domain??

Reply 3

booklover1313

Original post by lev0701

i got this question where f(x)=square root of 1-9x^2 -a<x<a
and i had to find the range to it
the first question was also to find a and i got a=1, and that should be the domain??

Yes, the domain is the range of x values, so if a =1, then the domain would be
-1<x<1

For the range, remember that the x squared means that any value below 0 has the same value as the positive value. So I would guess that you would find the range from the minimum x^2 value of 0 and the max value of 1. Then you can work out the range

Reply 4

RDKGames

Study Forum Helper

Original post by lev0701

i got this question where f(x)=square root of 1-9x^2 -a<x<a
and i had to find the range to it
the first question was also to find a and i got a=1, and that should be the domain??

a is not 1.

Domain is the region of x values that the function can be evaluated at.

If a=1 then you’re saying -1<x<1 so you’re saying e.g. x=2/3 is good for the function. But it’s not. Try evaluating square root of 1-9x^2 at x=2/3.