Question

Can you help with this?

Answer 1

The slope of the given line  = 1  so the slope of the line perpendicular to it will be -(1/1)  = -1.
It also passes through point (1, -1)  so we use the point slope equation

y - y1 = m(x - x1)

y - -1) = -1(x - 1)
y + 1 = -x + 1
y = - x    <--------- that's the answer