Question

Complete the equation of the line through (2, 1) and (5, -8).

Use exact numbers.

y = ___

Answer 1

y = -3x + 7

General Formulas and Concepts:

Pre-Algebra

Order of Operations: BPEMDAS

1. Brackets
2. Parenthesis
3. Exponents
4. Multiplication
5. Division
6. Addition
7. Subtraction

• Left to Right

Algebra I

Equality Properties

Slope Formula:
`\displaystyle m=(y_2-y_1)/(x_2-x_1)`

Slope-Intercept Form: y = mx + b

• m - slope
• b - y-intercept

Explanation:

Step 1: Define

Point (2, 1)

Point (5, -8)

Step 2: Find slope m

Simply plug in the 2 coordinates into the slope formula to find slope m

1. Substitute [SF]:
   `\displaystyle m=(-8-1)/(5-2)`
2. Subtract:
   `\displaystyle m=(-9)/(3)`
3. Divide:
   `\displaystyle m=-3`

Step 3: Find y-intercept b

1. Substitute in m [SIF]: y = -3x + b
2. Substitute in point: 1 = -3(2) + b
3. Multiply: 1 = -6 + b
4. Isolate b: 7 = b

Step 4: Write Equation

1. Substitute in b [SIF]: y = -3x + 7