For this case we have that by definition, a quadratic equation in its standard form is given by:
[tex]ax ^ 2 + bx + c = 0[/tex]
In this case we have the following equation:
[tex]-x ^ 2 + 4x-7 = 0[/tex]
So, according to the standard form we have:
[tex]a = -1\\b = 4\\c = -7[/tex]
Answer:
The value of c is -7.