[tex]y = (2-x)(1+3x)[/tex]
[tex] = 2 + 6x - x - 3x^{2}[/tex]
[tex] = 2 + 5x - 3x^{2}[/tex]
[tex]\frac{dy}{dx} = m = 5 - 6x[/tex]
At x = 1:
[tex]\frac{dy}{dx} = m = 5 - 6 = -1[/tex]
[tex]y - 7 = -(x - 1)[/tex]
[tex]y = -x + 8[/tex]
[tex]\therefore y = 8 - x[/tex]
