\(The\ slope-intercept\ form:y=mx+b\\\\The\ slope-point\ form:y-y_1=m(x-x_1)\\\\The\ slope:m=\dfrac{y_2-y_1}{x_2-x_1}\\---------------------\\(-1;\ 2);\ (2;-1)\\\\m=\dfrac{-1-2}{2-(-1)}=\dfrac{-3}{3}=-1\\\\y-(-1)=-1(x-2)\\y+1=-x+2\ \ \ |subtract\ 1\ from\ both\ sides\\\boxed{y=-x+1}\)
