Question

Find the equation of a straight line passingthrough the points (1, 1) and (2, -1).

Answer 1

Using two-points form equation of a line formula as shown below

`(y-y_1)/(x-x_1)=(y_2-y__1)/(x_2-x_1)`

From the question, we have that:

`\begin{gathered} (1,1)\rightarrow x_1=1,y_1=1 \\ (2,-1)\rightarrow x_2=2,y_2=-1 \end{gathered}`

Substitute the coordinates values above in the two-points form equation

`(y-1)/(x-1)=(-1-1)/(2-1)`
`(y-1)/(x-1)=(-2)/(1)`

Cross multiply and simplify the equation

`\begin{gathered} 1(y-1)=-2(x-1) \\ y-1=-2x+2 \\ y=-2x+2+1 \\ y=-2x+3 \end{gathered}`

Hence, the equation of the straight line is y = -2x + 3