f(x) = sqrt(x-5) ; f(-4)
2007-01-31 18:56:51 · 5 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
f(-4) = sqtr(- 4 - 5) = sqrt(-9)
sqrt(-9) can only be calculated by using Complex Numbers where i² is defined as i² = -1
f(-4) = sqrt(i²9) = 3i where 3i is a complex number.
2007-01-31 19:06:01 · answer #1 · answered by Como 7 · 0⤊ 0⤋
Replace x with -4 on both sides of the equation f(x) = sqrt(x-5).
This gives you f(-4) = sqrt(-4 - 5). If you can evaluate that, do so. If not, you can't.
2007-02-01 03:10:54 · answer #2 · answered by a r 3 · 0⤊ 0⤋
The value is 3i, three times the square root of -1. There is no significant simplification to be done. This is an example of what is called an imaginary or complex number. They are extremely useful in higher mathematics.
2007-02-01 03:29:38 · answer #3 · answered by Anonymous · 0⤊ 0⤋
this can't be evaluated in the real number set!
but I'm afraid that you may not be aware of complex number set!
it is signed as C, while real number set is signed as R
and in the complex number set, it defines i^2=-1
and i is the sham number!
so f(-4)=sqrt(-4-5)=sqrt(-9)=3i
test solution: (3i)^2=9i^2=9*(-1)=-9
solution: 3i
2007-02-01 03:22:38 · answer #4 · answered by happyrabbit 2 · 0⤊ 0⤋
DNE
the function does not exist for all x <5
2007-02-01 03:03:59 · answer #5 · answered by BIGDAWG 4 · 0⤊ 0⤋