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Unit 4B Day 3. Point-Slope. Warm-Up #3 . HW Check . Core Time. Writing equations of lines. Use slope-intercept form if you are given: The slope and the y-intercept Two ordered pairs (one of which is the y-intercept) Word Problems that have rates flat fees/one-time payments
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Unit 4B Day 3 Point-Slope
Writing equations of lines Use slope-intercept form if you are given: • The slope and the y-intercept • Two ordered pairs (one of which is the y-intercept) • Word Problems that have rates flat fees/one-time payments Use Standard form with WORD PROBLEMS only!! -- With two items that add up to a total
If you are given • The slope and a point (not the y-intercept) • Two ordered pairs (neither the y-intercept) Use the point-slope formula!!!
Point – Slope Formula If you know one point a line passes through and the slope of the line. Point Slope Formula: m = Slope is the ordered pair Y and x stay as the variable y and x * Never plug in for them!
Ex.1 A line passes through the point (3, 4) and has a slope of 2. Write the equation of the line:
2. Write the equation of the line that has a slope of -3 and passes through the point (-1,7).
Converting to Slope-Intercept Step1: Distribute Step2: Move the constant on the left to the right.
6. Write the equation of the line that has a slope of and passes through the point (5, -7). Make sure your final answer is in slope-intercept form.
a)Write an Equation of the line with: b) Change to Slope-intercept form 7. (-1, -3); Slope = 4 y + 3 = 4(x + 1) 8. (-10, 0); Slope = 2 y = 2(x +10) 9. (-4, 3); Slope = -6 y – 3 = -6(x +4)
a) Write an Equation in Point-Slope Form Given Two Pointsb) Change to slope intercept form 10. (-3, 6) and (1, -2) y – 6 = -2(x + 3) or y + 2 = -2(x – 1) 11. (-2, 3) and (-1, 1) y – 3 = -2(x + 2) or y – 1 = -2(x + 1) 12. (-2, -5) and (7, -6) y + 5 = - (x + 2) or y + 6 = - (x – 7)
Writing an Equation from a Table • What is the independent and dependent variable? x – independent; y – dependent • Find the rate of change: • What is the slope? 4/10 = 2/5 • What is one ordered pair? (-11, -7), (-1, -3), (4, -1), (19, 5) • What is a possible equation in Point-Slope Form? y + 7 = 2/5 (x + 11)
Example: Boiling Point of Water Is the relationship shown by the data in the table linear? If so, model the data with an equation. Step 1: Find the rates of change for each ordered pair. Step 2: Use the slope and a point to write an equation.
Step 1: Graph the ordered pair. Step 2: Starting at the ordered pair, use your slope to graph another point on the line.
Write the equation of the line in Point Slope Form Step 1: Find the slope Using the two points Step 2: Pick one of the Points. Step 3: Use step 1 and Step 2 to substitute into The point slope formula