What is the gradient of the blue line

yes the total will be same because in both of them the expression.is rearranged but their sign remains the same hence it hss just been shuffled

for this case we have by definition, if two lines are perpendicular, then the product of their slopes is -1.

then, given the following line:

so,

we are looking for m_ {2}:

then, the line is given by:

we find "b" replacing the given point:

finally, the equation is:

option c