Tell whether each expression is positive or negative for the line shown:

$\begin{array}{l}a.y_2-y_1\\ b.x_2-x_1\\ c.\frac{y_2-y_1}{x_2-x_1}\end{array}$

The given figure is:

We have to find whether given expression positive or negative.

From the given figure we see that the coordinate$\left(x_2,y_2\right)$ is in the first quadrant and$\left(x_1,y_1\right)$ is in the third quadrant.

So $x_2,y_2$are positive values and$x_1,y_1$ are negative values.

It means, the value of expression$y_2-y_1$ is positive.

Because$+ve-(-ve)=+ve+ve=+ve$ .

So, the expression$y_2-y_1$ is positive.

The given figure is:

We have to find whether given expression $x_2-x_1$positive or negative.

From the given figure we see that the coordinate$\left(x_2,y_2\right)$ is in the first quadrant and $\left(x_1,y_1\right)$is in the third quadrant.

So$x_2,y_2$ are positive values and$x_1,y_1$ are negative values.

It means, the value of expression$x_2-x_1$ is positive.

Because$+ve-(-ve)=+ve+ve=+ve$ .

So, the expression$x_2-x_1$ is positive.

The given figure is:

We have to find whether given expression $\frac{y_2-y_1}{x_2-x_1}$positive or negative.

From part a, the expression$y_2-y_1$ is positive.

From part b, the expression$x_2-x_1$ is positive.

So,$\frac{y_2-y_1}{x_2-x_1}=\frac{+ve}{+ve}=+ve$ .

It means$\frac{y_2-y_1}{x_2-x_1}$ is positive.