Given the equation
[tex]y=2x+51[/tex]
Notice that it is a linear equation
The change per day in the road's length is given by the slope of the line which is the constant that accompanies the x-term.
Therefore, the answer to part 1) is 2 miles.
On the other hand, set x=0 (zero days since the crew started working); then,
[tex]\begin{gathered} y=2\cdot0+51 \\ \Rightarrow y=51 \end{gathered}[/tex]
Thus, the initial length of the road is 51 miles.
