The values of that satisfy both of these equations:
are
- only 4
- -7 and 4
- 0 and 4
- no at all
- all real
Solution
Of course you can simply check the given answers. You can also graph the two equations. They yield the circle and parabola.
Or you can use algebra. From the second equation, we find that
This can be substituted into the first equation,
which is a mere quadratic equation whose roots are . But do these roots satisfy both equations?
The answer is (a).