After 2.0 years, the 4.0 mg sample decays to 2.0 mg.
After another 2.0 years (total 4.0 years), the 2.0 mg sample decays to 1.0 mg.
And after another 2.0 years (total 6.0 years), the 1.0 mg sample decays to 0.50 mg.
So it takes 6.0 years for 4.0 mg to decay to 0.50 mg.
Not always sometime depends what kind of problem your doing
X^2-2x -3 =0
a =1 b =-2 and c = -3
x = - (-2) +/- sqrt (-2)^2 - 4(1)(-3)
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2(1)
x = + 2 +/- sqrt [(4) - 4(-3)]
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2
x = +2 +/- sqrt [4 + 12]
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2
x = +2 +/- sqrt[16]
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2
x = +2 +/- (4)
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2
x = 2 + 4 or 2 -4
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2 2
x = 6/2 or -2/2
x = 3 or x = -1
1. diginity
2.require
3.tuition