# The coordinates of two vertices of square ABCD are A(2,1) and B(4,4). Determine the slope of side BC. Does this question require the use of point-slope form or something? And perpendicular lines?...

The coordinates of two vertices of square ABCD are A(2,1) and B(4,4). Determine the slope of side BC.

Does this question require the use of point-slope form or something? And perpendicular lines? Please explain in detail that is easy for me to understand.

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### 2 Answers

The slope of the line connecting two points with given coordinates can be found using the slope formula:

`m=(y_2 - y_1)/(x_2 - x_1)`

So the slope of AB will be

`m_(AB) = (y_B-y_A)/(x_B - x_A) = (4-1)/(4-2) = 3/2`

Since AB and BC are adjacent sides of a square, they are perpendicular to each other. The slopes of perpendicular lines are negative reciprocals, that is, they obey the relationship

`m_(AB)*m_(BC) = -1`

From here, `m_(BC)= -1/m_(AB) = -1/(3/2) = -2/3` ` `

**So the slope of BC is -2/3.**

### User Comments

This is easy

the slope of AB is = `(y2 -y1)/(x2-x1)` = `(4-1)/(4-2)` = `3/2`

As in the square all sides ae perpendicular to each other then

AB is perpendicular to BC so,

**(slope of AB)*(slope of BC)= -1**

**so,**

slope of BC= -1/(slope of AB)

= -1/(3/2)

**= `(-2)/3` **

:)

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