SOLUTION: Determine all values of c so that the lines cy+4x=9 and cy-5x=10 are perpendicular.

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Question 902044: Determine all values of c so that the lines cy+4x=9 and cy-5x=10 are perpendicular.
Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
Using knowledge of standard form equation for a line, ax+by=k will have slope -a%2Fb.

cy+4x=9 has slope -4%2Fc.

cy-5x=10 has slope 5%2Fc.

The two lines given to be perpendicular requires that the product of the slopes equals negative one, highlight_green%28-%284%2Fc%29%2A%285%2Fc%29=-1%29. Solve for c.

-20%2Fc%5E2=-1
20%2Fc%5E2=1
20=c%5E2
c=0%2B-sqrt%284%2A5%29
highlight%28c=0%2B-+2%2Asqrt%285%29%29.