Plans for a bridge are drawn on a coordinate grid. one girder of the bridge lies on the line y = 3x – 3. a perpendicular brace passes through the point (–7, 9). write an equation of the line that contains the brace.

Y = 3x - 3. The slope here is 3. A perpendicular line will have a negative reciprocal slope. This can be found by " flipping " the slope and changing the sign3 or 3/1" flip " ...becomes 1/3...change the sign...becomes -1/3. So ur perpendicular line will need a slope of -1/3.

y = mx + b
slope(m) = -1/3
(-7,9)...x = -7 and y = 9
now we sub and find b, the y int
9 = -1/3(-7) + b
9 = 7/3 + b
9 - 7/3 = b
27/3 - 7/3 = b
20/3 = b

so ur perpendicular line containing the brace is : y = -1/3x + 20/3