Answer:
Option 2 and 3 are not written in explicit form.
Step-by-step explanation:
We have four functions we have to find which one of them are not written in explicit form:
Explicit form is the form in which we can finc the value of n.
Option 1 is correct
y=x because
we can calculate y and x by substituting different values.
Option 2 is incorrect because we can not calculate y from the given equation
[tex]x^2-6xy-9y^2=0[/tex]
Option 3 is incorrect because y=0 we can not find anything.
Option 4 is correct because we can find values of y by substituting different values of x in the given equation that is [tex]y=-\sqrt{(1-x^2)[/tex].