Uma [b]função linear[/b] , trata - se de um caso particular da função afim onde b=0, e é definida, em linguagem matemática, por:[center][b][img width=65,height=18]data:image/png;base64,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[/img][/b][/center]onde:[br][list][*]a [math]\in\mathbb{R}[/math][/*][*]a[math]\ne[/math]0[/*][*]x[math]\in[/math][math]\mathbb{R}[/math][br][br][/*][/list]O gráfico da função linear é uma [b]reta[/b] que passa pela origem (0,0)[br][br]Observe os exemplos abaixo: