[tex]General\ equation\ for\ line\ in\ slope\ intercept\ form:\\\\y=ax+b\\\\To\ find\ a\ and\ b\ substitude\ points\ (3,9),\ (-2,-11)\ into\ equation\\\\ \left \{ {{9=3a+b}\ \ \ \ \atop {-11=-2a+b\ |*-1}} \right.\\\\ \left \{ {{9=3a+b}\ \ \ \ \atop {11=2a-b}} \right.\\+----\\\\Addition\ method\\\\20=5a\ \ |:5\\\\a=4\\ b=9-3a\\b=9-3*4=9-12=-3\\\\Answer\ y=4x-3
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