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# help line question

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Let line L1  be the graph of 5x + 8y= -13. Line L2 is perpendicular to line L1 and passes through the point (10, -10). If line L2 is the graph of the equation y = mx + b, then find m + b.

Dec 22, 2020

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Rearrange the L1 equation as $$y=-\frac{5}{8}x-\frac{13}{8}$$

The slope of L2 must be $$m=\frac{8}{5}$$ so its equation will be $$y=\frac{8}{5}x+b$$

We know it goes through point (10, -10), so  $$-10=\frac{8}{5}\times10+b$$

Can you take it from here?

Dec 22, 2020