Question 752573
Hello, 
We could set these equations 5x + 3y = 9 and -3x + 5y = 10 as y=mx+b and then can determine. 
y =-5/3x+3 
y =3/5x+2
We can see that these equations are perpendicular since the slope is a negative reciprocal. 
Make sense?
RJ
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