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Use the quadratic formula to solve : 0.7x^2-4.2x-0.7=0

Use the quadratic formula to solve : 0.7x2-4.2x-0.7=0
The solution set is {_}

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Arturo O. | Experienced College Instructor for Physics TutoringExperienced College Instructor for Physi...
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I would first simplify the equation by dividing through by 0.7, which gives:
 
x^2 - 6x -1 = 0
 
Then by the quadratic formula,
 
x = {-(-6) +/-sqrt[(-6)^2 - 4(1)(-1)]} / 2 = {6 +/-sqrt(40)] / 2 = 3 +/-sqrt(10)
 
You get two real roots:
 
x1 = 3 + sqrt(10)
x2 = 3 - sqrt(10)