Slope-intercept form?

Question

Write the equation of the line in slope-intercept form given the following information:

(-9,9), (0,1)

Answer 1

This means that line is passing through (-9,9) & (0,1).

Now slope-intercept form of eqn of line is

y = mx + c, where m is the slope of the line, and c is the y-intercept{length of y-axis cut out by the line with respect to origin})

Step 1 - Calculate m

m = (Y2 - Y1) / (X2 - X1)

m = (1 + 9) / (0 - 9)

=> m = -10 / 9

Equation has now become, y = (-10/9)x + c .... (i)

Step 2 - Calculate c

For this put y = 1 and x = 0 in (i), (we are substituting the point (0,1) coordiantes)

It will become, 1 = (-10/9)*0 + c

=> c = 1

Now, finally, equation of line in slope-intercept form is

y = (-10/9) * x + 1

[ Note that you can apply any method to get the equation of line, but finally give it a slope-intercept form by multiplying and dividing the equation by suitable constants ]