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# equation of line

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Line $\ell_1$ represents the graph of $3x + 2y = -14 - 8x + 5y$.  Line $\ell_2$ passes through the point $(5,-6)$, and is perpendicular to line $\ell_1$.  Write the equation of line $\ell_2$ in the form $y=mx +b$.

Oct 24, 2023

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First, we can put $$\ell_1$$ into slope intercept form.

3x + 2y = -14 - 8x + 5y

3 y - 11 x = 14

y = 11x/3 + 14/3

Now, if a line is perpendicular to another, their slopes are negative reciprocals of each other. Since $$\ell_1$$ has a slope of 11/3 and is perpendicular to $$\ell_2$$, $$\ell_2$$ will have a slope of -3/11. Plugging this m-value into our slope intercept form y = mx + b yields y = -3x/11 + b. Because (5, -6) is a point on $$\ell_2$$, we can plug the x and y-values into the equation to solve for b.

y = -3x/11 + b

(-6) = -3(5)/11 + b

-6 = -15/11 + b

66 = 15 - 11b

11b = -51

b = -51/11

Plug the value of b back into our equation to get the final equation of $$\ell_2$$$$y = -\frac{3}{11}x - \frac{51}{11}$$

Oct 25, 2023
edited by knotW  Oct 25, 2023