standard form of an equation can be represented by ax^2 + bx + c = y. where a b are coeficients and c is a constant value. for your equation to work we have to say:
a = -1
b = 4
c = -7
you have to be sure to put the negative value. if i said
a = 1
b = 4
c = 7
and i plugged these in i would get:
(1)x^2 + (4)x + (7)
which becomes
x^2 + 4x + 7
this is not right. if i used the first values i stated then:
(-1)x^2 + (4)x + (-7)
-x^2 + 4x - 7
this is correct