First, we'll move all terms to one
side:
21x^2 + 22x - 8 =
0
We'll use the quadratic formula to factorize the
equation:
21x^2+22x-8=0
x1 =
[-b +/- sqrt(b^2 - 4ac)]/2a
We'll identify the coefficients
a,b,c:
a = 21
b =
22
c = -8
b^2 - 4ac = 484 +
672
sqrt (b^2 - 4ac) = sqrt
1156
sqrt (b^2 - 4ac) = 34
x1
= (-22+34)/2*21
x1 = 12/42
x1
= 6/21
x2 = (-22-34)/2*21
x2
= -56/42
x2 = -28/21
We can
now factorize the quadratic:
21x^2+22x-8 = 21(x - x1)(x -
x2)
We'll substitute x1 and
x2
21x^2+22x-8 = 21(x - 6/21)(x +
28/21)
or
21x^2+22x-8
= (21x - 6)(21x + 28)
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