Linear Equations and Their Forms

Linear equations have variables with powers of 1, while non-linear equations have variables with other powers or are multiplied together. For example, "-3x+5=y" is linear, but "y=x²-8" is non-linear because x is squared.

There are several important forms of linear equations you need to know:

• Standard Form: Ax + By = C (where A, B, C are integers and A ≥ 0)
• Point-Slope Form: y - y₁ = m$x - x₁$ (where m is the slope and (x₁,y₁) is a point on the line)
• Slope-Intercept Form: y = mx + b (where m is the slope and b is the y-intercept)

The x-intercept is where the line crosses the x-axis (also called zeros, roots, or solutions), while the y-intercept is where it crosses the y-axis. You can identify if an equation is linear by checking if all variables have power of 1 and aren't multiplied together.

💡 When trying to determine if an equation is linear, look for variables with exponents other than 1 or variables multiplied together (like xy) - these make the equation non-linear!

Working with Linear Equations

Let's analyze the equation 3x - y = 8:

In standard form, we identify that A = 3, B = -1, and C = 8. Finding intercepts helps us graph the equation and understand its behavior.

To find the x-intercept, set y = 0 and solve for x: 3x - 0 = 8 3x = 8 x = 8/3 So the x-intercept is $8/3, 0$

For the y-intercept, set x = 0 and solve for y: 3(0) - y = 8 -y = 8 y = -8 So the y-intercept is $0, -8$

⚠️ Be careful with signs when rearranging equations! A common mistake is forgetting to change signs when moving terms from one side to another.

Converting Between Forms

When working with fractions in linear equations, you can multiply all terms by a common denominator to eliminate fractions. This makes the equation easier to work with.

For example, with ¼x + ⅘y = 4, we can multiply all terms by 20 (the LCM of 4 and 5): 5x + 16y = 80

Now we can easily identify the standard form values: A = 5, B = 16, C = 80.

Finding intercepts follows the same process as before:

• For the x-intercept: set y = 0, which gives us 5x = 80, so x = 16, making the point (16, 0)
• For the y-intercept: set x = 0, which gives us 16y = 80, so y = 5, making the point (0, 5)

🌟 Converting equations to standard form makes them easier to graph and analyze, especially when dealing with fractions!

Converting to Standard Form

Converting different equation types to standard form follows specific steps depending on the original form.

For equations like x - 3 = 9, first rearrange to isolate the variable: x - 3 = 9 x = 12 This is now in the form x = 12, which technically isn't standard form, but tells us the line is vertical at x = 12.

For equations with decimals like -0.15x - 0.72 = 19y, multiply by 100 to eliminate decimals: -15x - 72 = 19y Then rearrange to standard form: 15x + 19y = -72

🔑 When converting to standard form, remember that A should be positive. If you get a negative A value, multiply the entire equation by -1 to fix it!