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Name:__________________________________________ Date:______________________ Period:________ Algebra 2 Section 2-4 Day 2 More About Linear Equations Writing Equations of Lines The 3 forms of an equation of a line are: Slope-Intercept Form Point-Slope Form Standard Form y mx b y y1 m( x x1 ) Ax By C Use this form when you know the Use this form when you know the A, B, and C are real numbers. A ______________ and the _____________ and a _________, and B cannot both be __________________. or when you know ____________. _____________. What is the equation of the line y y 3 x 5 in standard form? Use integer coefficients. 4 3 x5 4 Write the equation of a line in standard form with integer coefficients. 1. y 1 x2 2 2. y 7 x 9 3. y 3 x3 5 4. y 4.2 7.9 To write the equation of line: Pick the form that matches the information you are given { y mx b or y y1 m( x x1 ) } Substitute given information into the corresponding equation Solve equation for the appropriate form in the directions Given two points: o Find the slope o Pick a point o Use point-slope to write the equation of the line Given a graph: o Find your y-intercept (b) and slope (m) Examples: I. Write an equation of the line in slope-intercept form of each line described. 1. slope 2; y-intercept 15 ____________________ 1 2 2. slope ; y-intercept 3 2 ____________________ 3. slope –3, (–1, 2) ____________________ II. Write an equation of the line in standard-form form of each line described. 4. slope 0 , through (1, –4) ____________________ 5. (4, –3) and (3, –6) ____________________ 6. vertical line through (9, –15) ____________________ III. Write an equation of the line in point-slope form of each line described. 7. slope 1 , through (2, –5) 4 8. (5, –12) and (0, –6) ____________________ 9. horizontal line through (1, 2) ____________________ ____________________ Write an equation of the line in slope-intercept form of each line graphed. 10. 11. ___________________ 12. ___________________ ____________________