Question

what is the equation in standard form of the line which passes through (-2,6) and has a slope of -1

Answer 1

y=mx+b
6=-1(-2)+b
6=2+b
b=4

So, equation of a line is:
y=-1x+4???
Is this what you need?

Answer 2

x-y=-4
x-y=4
x+y=4
x+y=-4

Answer 3

Standard form of a line is Ax + Bx = C
x+y=4