7x + 5y = -1 get: y = mx + c firstly, subtract 7x from both sides: 5y = -7x -1 divide both sides by 5: y = (-7x -1)/5: y= -7x/5 -1/5 therefore the slope, m = -7/5 in the formula y = mx + c perpendicular test m1 .m2 = -1 m1 = -7/5, substitute in formula: (-7/5) x m2 = -1 m2 = -1 /(-7/5) which equals [ invert and multiply] -1 x -5/7 = 5/7 perpendicular slope m2 = 5/7 new line y=mx +c is: y = 5/7 x -1/5
