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In this lesson we will write linear equations in standard form. This equation is in slope-intercept form:. y = - ½ x + 6. This equation can be re-arranged another way so that x and y are together, and the fraction is eliminated.
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In this lesson we will write linear equations in standard form
This equation is in slope-intercept form: y = - ½ x + 6 This equation can be re-arranged another way so that x and y are together, and the fraction is eliminated.
To put x and y on the same side of the equation, we can add ½x to both sides. y = - ½ x + 6 ½x + y = 6 What number would be multiplied by both sides to eliminate the fraction?
To eliminate the fraction, we multiply each side of the equation by 2 y = - ½x + 6 2[½x + y] = [6]2 x + 2y = 12
Now x and y are on the left side of the equation, and the fraction has been eliminated x + 2y = 12 Linear Equations that follow this pattern are in standard form. Ax + By = C
Let’s write another equation in standard form: y = ¾x + 2 Both x and y should be on the left side of the equation in standard form. What should be done first?
¾x should be subtracted from both sides to ‘move’ the x to the left side of the equation y = ¾x + 2 - ¾x + y = 2 An equation in standard form contains no fractions or decimals. How can we eliminate the fraction in this equation?
Multiply by 4 to eliminate the fraction - ¾x + y = 2 4[- ¾x + y] = [2]4 -3x + 4y = 8
Since the equation has a negative in the first term, it can be eliminated by multiplying both sides of the equation by -1 -3x + 4y = 8 -1[-3x + 4y] = -1[8] 3x – 4y = -8 This step isn’t required, but on a multiple choice exam, you would need to perform this extra step if you don’t find the first equation.
Write this equation in standard form How do we ‘move’ x to the left side?
Add the term containing x to both sides (since it is negative)
Write this equation in standard form y = -2.5x – 3 Add 2.5x to both sides
Write this equation in standard form y = -2.5x – 3 2.5x + y = -3 Now eliminate the decimal
Multiply by 10 to remove the decimal 2.5x + y = -3 10[2.5x + y] = [-3]10 25x + 10y = -30 Let’s graph this equation using x and y intercepts
Use zeros in the table to find x and y intercepts 25x + 10y = -30
Graph the two pointsand connect 25x + 10y = -30
Complete Activity 5c • Write equations in standard form and slope-intercept form • Graph equations in standard form and slope-intercept form • Identify equations in standard form and slope-intercept form