The slope of a line
Given two points through which a line passes A(x1,y1), B(x2,y2), the slope of the line can be calculated with the formula:
![m=(y_2-y_1)/(x_2-x_1)](https://img.qammunity.org/2023/formulas/mathematics/high-school/78uaqhwt0aws3qfwxigaftpihnmb1gzxtp.png)
We are given the point A(-4,-8) and the (incomplete) point B(?,1). Knowing the slope is m=2, we can calculate the missing value at point B. Let's call it x: B(x,1).
Substituting all the values in the formula of the slope, we get:
![2=(1-(-8))/(x-(-4))=(9)/(x+4)](https://img.qammunity.org/2023/formulas/mathematics/college/e4s1y5tf5hw8essfn586h0q9bga9c8lv4k.png)
Operating:
![\begin{gathered} 2(x+4)=9 \\ 2x+8=9 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/m7z51sln6eeys8ug6t0mdwhayv7ahzm7vv.png)
Solving for x:
![\begin{gathered} 2x=9-8=1 \\ x=(1)/(2) \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/intb3i6ruoozdqwxugqb8p8rru2xhx72lp.png)
The missing value is 1/2, thus point B is B( 1/2 , 1 )