To write a slope intercept equation you need the slope and the y intercept which is b. The slope of y=x is 1 and to find a perpendicular slope you flip it and make it the opposite sign so in this case is would still be 1\1 but now it will be negative so your slope is -1 and you plug in 2 for x and 2 for y into the equation y=mx+b and m=your slope (which is -1) to find the value of b. so you get y=-1(2)+b. When you solve you get b=4 and then rewrite the intercept slope equation which is y=mx+b and plug in your slope for m and 4 for b so your final answer is y=-1x+4
