SOLUTION: I would love some help on this one. Particularly the graphing. Solve the following quadratic equations. Make sure to show all your work. Do not use any method (e.g., factoring,

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons -> SOLUTION: I would love some help on this one. Particularly the graphing. Solve the following quadratic equations. Make sure to show all your work. Do not use any method (e.g., factoring,       Log On


   

Question 100707: I would love some help on this one. Particularly the graphing.
Solve the following quadratic equations. Make sure to show all your work. Do not use any method (e.g., factoring, completing the square, quadratic formula, graphing) more than twice. Use the graphing method at least once.
1. 3x2 + 11x – 20 = 0
2. x2 + 3x – 4 = 0
3. 3x2 – x – 1 = 0
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Do not use any method (e.g., factoring, completing the square, quadratic formula, graphing) more than twice. Use the graphing method at least once.
1. 3x^2 + 11x – 20 = 0
Factor:
= 3x^2+15x-4x-20
= 3x(x+5)-4(x+5)
= (x+5)(3x-4)
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2. x^2 + 3x – 4 = 0
Complete the square:
x^2+3x+(3/2)^2 = 4 + (3/2)^2
(x+(3/2))^2 = 25/4
x+(3/2) = 5/2 or x+(3/2)=-5/2
x=1 or x = 4
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3. 3x^2 – x – 1 = 0
Graphing:
graph%28400%2C300%2C-10%2C10%2C-10%2C10%2C3x%5E2-x-1%29
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Cheers,
Stan H.