Please help me on this. On my homework I have the problem

Forums Algebra Please help me on this. On my homework I have the problem

This topic contains 6 replies, has 5 voices, and was last updated by Avatar of ÜberMathGuru ÜberMathGuru 2 years, 5 months ago.

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February 23, 2012 at 5:07 pm #428 Close | Stick (to front) | Merge | Trash | Spam | Reply
Avatar of kelman90
kelman90
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Given x^2+bx+2c=0

What value in terms of c must b have to make this expression a perfect square?

March 7, 2012 at 10:48 am #455 Move | Split | Trash | Spam | Reply
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Yeah
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polonium-210 is a radioactive element with a half-life of 140 days. This means that half of the polonium decays every 140 days. If 400 mg is the initial sample how much is left after 700 days?

March 7, 2012 at 10:48 am #456 Move | Split | Trash | Spam | Reply
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Yeah
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and what is the formula?

March 13, 2012 at 6:44 pm #471 Move | Split | Trash | Spam | Reply
Avatar of ÜberMathGuru
ÜberMathGuru
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Yeah,

Sorry for the delayed response!

The basic equation for half life is

AT = A0 2^(-T/H)

where A0 is the initial radioisotope’s activity, AT is the decayed activity after time T, and H is the half-life.

These values in your problem would be:

A0=400 mg
H=140 days
T=700 days

and AT is what they are asking for.

AT=400x[2^(-700/140)]=400×2^(-5)= 400x (1/2^32) = 400/32= 12.5 mg

March 16, 2012 at 9:00 pm #478 Move | Split | Trash | Spam | Reply
Avatar of butler
butler
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what are all the variables of a graph

March 21, 2012 at 8:05 pm #487 Move | Split | Trash | Spam | Reply
Avatar of ÜberMathGuru
ÜberMathGuru
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(x^2y^-4)^2=x^4y^-8

Always multiply the outer exponent by the exponent of each factor (or by both the exponent of the numerator and the denominator if it is a ratio)!!!!

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