How do you solve the equation 3x^2+6x-1=8?

1 Answer
YouDid
Feb 4, 2015

You want an equation like ax^2+bx+c=0, so we subtract 8 from both sides. We now get 3x^2+6x-9 = 0, so we find a=3, b=6 and c=-9.
We use the quadratic formula to solve this equation:
D=b^2-4ac = 6^2-4*3*-9 = 36+108=144.
We know that x=(-b+-sqrt(D))/(2a) = (-6+-sqrt(144))/(2*3) = (-6+-12)/6= -1+-2, so x=1 vee x=-3.

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