Đáp án:
\(\eqalign{
& a)\,\,y = 2x - 5 \cr
& b)\,\,y = - 1. \cr} \)
Giải thích các bước giải:
\(\eqalign{
& y = ax + b \cr
& a)\,\,Di\,\,qua\,\,A\left( {4;3} \right) \Rightarrow 3 = 4a + b \cr
& \,\,\,\,\,Di\,\,qua\,\,B\left( {2; - 1} \right) \Rightarrow - 1 = 2a + b \cr
& \Rightarrow \left\{ \matrix{
4a + b = 3 \hfill \cr
2a + b = - 1 \hfill \cr} \right. \Leftrightarrow \left\{ \matrix{
a = 2 \hfill \cr
b = - 5 \hfill \cr} \right. \cr
& \Rightarrow y = 2x - 5 \cr
& b)\,\,Song\,\,song\,\,voi\,\,Ox \Rightarrow a = 0 \Rightarrow y = b \cr
& Di\,\,qua\,\,A\left( {1; - 1} \right) \Rightarrow - 1 = b \cr
& Vay\,\,y = - 1. \cr} \)
