Which of the following could not be points on the unit circle

B and C cannot be points on the unit circle

Step-by-step explanation:

This like asking which of the points does not satisfy x^2+y^2=1.

Let's look at (-2/3 , sqrt(5)/3)

x=-2/3

y=sqrt(5)/3

We have x^2=4/9 while y^2=5/9, and x^2+y^2=4/9+5/9=9/9=1.

This first one looks great and is on the unit circle.

Let's look at (sqrt(3)/2 , 1/3)

x=sqrt(3)/2

y=1/3

We have x^2=3/4 and y^2=1/9 , and x^2+y^2=3/4+1/9=31/36 (this is not 1).

This point is not on the unit circle.

Let's look at (1,1)

x=1

y=1

We have x^2=1 and y^2=1, and x^2+y^2=1+1=2 (this is not 1).

This point is not on the unit circle.

Let's look at (0.8,-0.6)

x=0.8

y=-0.6

We have x^2=.64 and y^2=.36, and x^2+y^2=.64+.36=1

This point is on the unit circle.

step-by-step explanation: