Question 912913
{{{f(x)= (5/2)x+3}}} => slope is {{{(5/2)}}} and  a line perpendicular to the following line has a slope negative reciprocal

so, the slope of a perpendicular line is {{{-1/(5/2)}}} =>{{{ -2/5 }}}


check with these lines: {{{f(x)= -(2/5)x+3}}} or {{{f(x)= -(2/5)x}}} (they have same slope and they are parallel to each other, and both should be perpendicular to  {{{f(x)= (5/2)x+3}}})

{{{ graph( 600, 600, -10, 10, -10, 10, (5/2)x+3, -(2/5)x,-(2/5)x+3) }}}