x - 3y = 9 can be rewritten in y = mx + b notation as y = x/3 - 3. The slope of this line (m) is 1/3. To find the slope of a perpindicular line, multiply m by negative one and take the reciprocal. So the slope of the new perpindicular line would be -3.
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6x+3y = -9 3y = -6x-9 y = -2x-3 Therefore the perpendicular slope is 1/2
Put in function, Y = mX + C, form. 6X + 3Y = - 9 3Y = - 6X - 9 Y = - 2X - 3 -------------------- m(slope) = - 2 ----------------------
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With a line in the form y = mx + c, it has gradient m and the line perpendicular to it has gradient m' such that mm' = -1, ie m' = -1/m. A line through a point (x0, y0) with gradient m' has an equation of: y - y0 = m' (x - x0) which can be rearranged to a form for y = mx + c. Thus for the line 2x - 3y = 7: 2x - 3y = 7 → 3y = 2x + 7 → y = 2/3 x + 7/3 → it has gradient 2/3 → perpendicular line has gradient -3/2 → perpendicular line through (4, 9) perpendicular to 2x - 3y = 7 has equation: y - 9 = (-3/2)(x - 4) → 2y - 18 = -3(x - 4) → 2y - 18 = -3x + 12 → 2y = 30 - 3x → 3x + 2y = 30
The "point slope" formula would be used. This is Y-Y1=m(X-X1) where Y1 and X1 are points the line passes through. M is the slope, so to find the slope of a line perpendicular, take it's opposite reciprocal which would be -8x/9. So Y-(-8)=-8/9(X-18) distribute -8/9 into X-18 and add the 8 on the left side of the = to get the slope intercept form.