Solver Find the equation of line going through points

Source code of 'Find the equation of line going through points'

This Solver (Find the equation of line going through points) was created by by MathLover1(20849)

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==section input
Find the equation of line going through points 
(*[input x1=1], *[input y1=2])  and (*[input x2=0], *[input y2=1]).
==section solution
perl

$slope = 0;

print "haha";

if( $x1 == $x2 ) {
  print "Error, the x coordinates of both points are the same. That cannot describe a non-vertical line. Please enter different x values.";
  return undef;
} else {
  $slope = ($y2-$y1)/($x2-$x1);
  $intercept = $y1-$slope*$x1;
  print "We are trying to find equation of form y=ax+b, where a is slope, and b is intercept, which passes through points (x1, y1) = ($x1, $y1) and (x2, y2) = ($x2, $y2).
Slope a is {{{a = (y[2]-y[1])/(x[2]-x[1]) = ($y2-$y1)/($x2-$x1) = $slope}}}.
Intercept is found from equation {{{a*x[1]+b = y[1]}}}, or {{{$slope*$x1 +b = $intercept}}}. From that, 
intercept b is {{{b=y[1]-a*x[1]}}}, or {{{b=$y1-$slope*$x1 = $intercept}}}.

y=($slope)x + ($intercept)

Your graph:

{{{
drawing(600, 600, -30, 30, -30, 30,
  graph( 600, 600, -30, 30, -30, 30, $slope*x+$intercept ),
  red( locate( $x1, $y1, \"$x1, $y1\" ), circle( $x1, $y1, 0.15 ) ),
  green( locate( $x2, $y2, \"$x2, $y2\" ), circle( $x2, $y2, 0.15 ) )
)
}}}
";
}

==section output
slope
intercept

==section check
  x1=1 y1=1 x2=2 y2=3 slope=2 intercept=-1

==section practice
perl
  $x1 = randint( -5, 2 );
  $y1 = randint( -5, 5 );
  $x2 = $x1+randint( 1, 5 );
  $y2 = $y1 + ($x2-$x1)*randint( -3, 3 );