miah
Solve. 5x2 – 20 = 0
x = 5 and x = 4
x = 4 and x = 2
x = –5 and x = 20
x = 2 and x = –2
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miah
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@RadEn
waterineyes
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You can start by:
Dividing both the sides by 5..
miah
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5x^2-4=0
RadEn
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x^2 - 4 = 0
RadEn
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factorize by using the difference squares formula
a^2 - b^2 = (a+b)(a-b)
waterineyes
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And you can use here :
\[x^2 - a^2 = (x + a) (x - a)\]
waterineyes
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Or if you don't wanna do this, then add 4 both the sides and then take square root both the sides.
miah
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so,... whats the answer ?
miah
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@RadEn
miah
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its not B
miah
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@waterineyes
waterineyes
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Who told you that answer is B?
waterineyes
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\(x^2 - 4 = 0\)
Add 4 both the sides and tell me what did you get?
RadEn
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well, look at how the factorization works
x^2 - 4 = 0
x^2 - 2^2 = 0
use the diff square formula,
(x+2)(x-2) = 0
solve for x
find the zeroes by make each factor be zero
first, x+2=0
subtract by 2 from both sides,
x+2-2 = 0-2
x = -2
do for the rest!
miah
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I dont really have to do the rest because there isnt another -2 in the other choices.
RadEn
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hehe, good tricky :)
waterineyes
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do for the rest is actually for your own knowledge and not for answer choices you are given with..
RadEn
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ok, show to us how to solve of
x - 2 = 0 ?