Which of the following is the best example of a definition?

There is a line with slope 1/a going through the point (a, a²). find the equation of the line perpendicular to this line at this point. (don’t let this problem intimidate you! solve the problem as you would if i’d given you specific values. just use variables instead.)

The square root of 9x plus 7 plus the square rot of 2x equall to 7

Ade and abc are similar. which best explains why the slope of the line between points a and d is the same as the slope between points a and b?