Slope Intercept y = mx+b

SLOPE INTERCEPT FORM

OK, everyone has worked with the graph of a line in the XY Plain; where y is the vertical axis & x is the horizontal axis.

The standard form of a line is written y = mx + b. There will probably be only one or two problems on your SAT that requires using this wonderful knowledge from several years ago. But it is not rocket science & if you spend a few minutes working on it, most of the rust will be removed and you will get these questions.

Warning: The questions can be tricky, so practice reading the wording and then try to ask yourself all of the different ways that a slope question can be asked. They can be easy medium or hard. Do not over-think the easy questions, they really are easy. But most of the examples in the BBP have medium and hard problems.

Y & X are coordinate points in the plain. m and b are constants, where m is the slope and b is the y intercept.

m - “SLOPE = RISE/RUN.” Slope is the ratio of the change in y to the change in x.

The numeric value of m is determined by how many units of y increase for every increase in units of x.

GIVEN TWO POINTS: x₁,y₁ & x₂, y₂ are points on the line. Calculate slope, m using the formula: (y₂-y₁)/(x₂-x₁)

b – “Y Intercept”

The value of b is the value of y when x=0. If the line passes through the origin (0,0), then b = 0. This can be a trick in a slope question.

Parallel & Perpendicular.

Parallel lines have the same slope with a different y intercept. (If they had the same intercept, they are NOT parallel, they are the SAME).

Perpendicular lines have a slope that is “the opposite inverse.” -1/m

Reflection is another issue that I will cover later.

Here are the problems in the BBP regarding slope intercept form.

Page #

399 14

487 2

522 17

672 12

682 11

736 14

745 9

775 4

Know what a line looks line when m = + or - & b = + or –

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