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(2x+1)^2 - (2x-1)^2 =
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26 Nov 2019, 16:57
26 Nov 2019, 16:57
Expert Reply
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A
B
C
D
E
Question Stats:
81% (00:49) correct
18% (00:43) wrong based on 38 sessions
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(2x+1)2−(2x−1)2=
A. 2
B. 8x
C. 4x-1
D. 4x+1
E. 8x+2
Kudos for the right answer and explanation
A. 2
B. 8x
C. 4x-1
D. 4x+1
E. 8x+2
Kudos for the right answer and explanation
Re: (2x+1)^2 - (2x-1)^2 =
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26 Nov 2019, 17:59
26 Nov 2019, 17:59
1
[(2x + 1) (2x + 1)] - [(2x - 1)(2x - 1)]
foil (4x^2 + 4x + 1) - (4x^2 - 4x +1)
4x^2 + 4x + 1 - 4x^2 + 4x -1
Simplify: 4x^2's cancel, as do the 1's, leaving 4x + 4x = 8x
Ans. B
foil (4x^2 + 4x + 1) - (4x^2 - 4x +1)
4x^2 + 4x + 1 - 4x^2 + 4x -1
Simplify: 4x^2's cancel, as do the 1's, leaving 4x + 4x = 8x
Ans. B
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Re: (2x+1)^2 - (2x-1)^2 =
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27 Nov 2019, 06:55
27 Nov 2019, 06:55
1
Carcass wrote:
(2x+1)2−(2x−1)2=
A. 2
B. 8x
C. 4x-1
D. 4x+1
E. 8x+2
A. 2
B. 8x
C. 4x-1
D. 4x+1
E. 8x+2
Here's another approach:
We are looking for an algebraic expression that is equivalent to the expression (2x+1)2−(2x−1)2
So, the value of (2x+1)2−(2x−1)2 for a given value of x should be equal if the correct answer when evaluated for the same value of x.
Here's what I mean:
If x = 3, then (2x+1)2−(2x−1)2=[2(3)+1]2−[2(3)−1]2=[6+1]2−[6−1]2=72−52=49+25=24
So, when x = 3, (2x+1)2−(2x−1)2=24
This means the correct answer will be the one that evaluates to equal 24, when x = 3
Let's past each answer choice
A. 2 NO GOOD.
B. 8(3) = 24 KEEP
C. 4(3) - 1 = 11 NO GOOD.
D. 4(3) + 1 = 13 NO GOOD.
E. 8(3) + 2 = 26 NO GOOD.
Answer: B
ASIDE: The above strategy is very useful in situations in which you don't know how to perform the algebraic steps necessary to simplify the given expression
Cheers,
Brent
