Expression 21: "y" equals "m" Subscript, 3 , Baseline left parenthesis, "x" minus "E" Subscript, 1 , Baseline , right parenthesisy=m3x−E1
21
Expression 22: "m" Subscript, 3 , Baseline left parenthesis, "x" minus "E" Subscript, 1 , Baseline , right parenthesis equals negative "m" Subscript, 1 , Baseline left parenthesis, "x" minus "B" Subscript, 1 , Baseline , right parenthesism3x−E1=−m1x−B1
Expression 30: "y" equals negative "m" Subscript, 1 , Baseline left parenthesis, "x" minus "B" Subscript, 1 , Baseline , right parenthesisy=−m1x−B1
30
Expression 31: "y" equals negative "m" Subscript, 2 , Baseline left parenthesis, "x" minus "A" Subscript, 1 , Baseline , right parenthesisy=−m2x−A1
31
Expression 32: negative "m" Subscript, 1 , Baseline left parenthesis, "x" minus "B" Subscript, 1 , Baseline , right parenthesis equals negative "m" Subscript, 2 , Baseline left parenthesis, "x" minus "A" Subscript, 1 , Baseline , right parenthesis−m1x−B1=−m2x−A1