def deltay(y2, y1)
  #puts "Delta y=#{y2 - y1}"
  y2 - y1
end

def deltax(x2, x1)
  #puts "Delta x=#{x2- x1}"
  x2-x1
end

def m(vardeltay, vardeltax)
  #puts "m=#{vardeltay / vardeltax}"
  vardeltay / vardeltax
end

def n(gradient, varx, vary)
 vary-gradient*varx
end

#activate the lines 21-25, when n is given.
#puts "Welcome to my linear function script. Please start with telling me your n:"

#print "> " ; n=STDIN.gets.to_i

#puts "So your n is #{n}."


puts "The first thing I need is your m.Please input your y2 then press RETURN and enter your y1:"
print "> " ; vary2=STDIN.gets.to_i ; vary1=STDIN.gets.to_i ; deltay(vary2, vary1)

puts "Now, please input your x2 then press RETURN and enter your x1:"
print "> " ; varx2=STDIN.gets.to_i ; varx1=STDIN.gets.to_i ; deltax(varx2, varx1)

puts "n"

puts "Your m equals #{m(deltay(vary2, vary1), deltax(varx2, varx1))}"

varm=m(deltay(vary2, vary1), deltax(varx2, varx1))

puts "So, now we need n. Your current equalation looks like this:y=#{varm}m+n"
puts "Lets insert your point, you gave me earlier : P(#{varx2}, #{vary2})"
puts "So, that is:"
puts "#{vary2}=#{varm*varx2}+n nNow we going to perform |-#{varm*varx2}. And that equals #{n(varm, varx2, vary2)}"  ; n=n(varm, varx2, vary2) #{#{vary2-(varm*varx2)}=n" ; n=vary2-(varm*varx2)}

puts "So this is our equation so far:"
puts "f(x)=#{varm}x+#{n}"

puts "Now let's get to y, okay? So I need a value for x:"
print "> " ; varx=STDIN.gets.to_i ; puts "y=#{varm*varx+n}"