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Bunuel
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For real numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5) 26 Mar 2019, 05:21
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A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!

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5% (low)

Question Stats:

90% (01:02) correct 10% (01:18) wrong based on 124 sessions

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For numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5) ?

(A) -72
(B) -27
(C) -24
(D) 24
(E) 72
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A
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For real numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5) 26 Mar 2019, 06:54
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Following the steps through we get first 3?(-9) and as a result -72.

Answer A
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For real numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5) 26 Mar 2019, 08:01
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4?5 is -9 and 3?-9 (9-81, x^2-y^2) gives -72. Option A

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For real numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5) 26 Mar 2019, 11:15
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Bunuel
For numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5) ?

(A) -72
(B) -27
(C) -24
(D) 24
(E) 72

solve for the expression as per expression we get
3?(-9)
then
-72
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For real numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5) 27 Mar 2019, 19:11
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Bunuel
For numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5) ?

(A) -72
(B) -27
(C) -24
(D) 24
(E) 72


We see that x?y is x^2 - y^2,

Thus, 4?5 = 4^2 - 5^2 = 16 - 25 = -9, and therefore,

3?(-9) = 3^2 - (-9)^2 = 9 - 81 = -72

Answer: A
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For real numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5) 21 Jun 2022, 02:58
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For numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5) ?

(A) -72
(B) -27
(C) -24
(D) 24
(E) 72

Based on the instruction, it will be = 3?(-9) = -72
Answer: A
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For real numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5) 21 Aug 2022, 11:33
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Given that x?y = (x + y)(x - y) and we need to find the value of 3?(4?5)

Let's start by finding the value of 4?5

To find 4?5 we need to compare what is before and after ? in 4?5 and x?y

=> We need to substitute x with 4 and y with 5 in x?y = (x + y)(x - y) to get the value of 4?5

=> 4?5 = (4 + 5)(4 - 5) = 9*-1 = -9

=> 3?(4?5) = 3?-9 = (3 + (-9))(3 - (-9)) = (3 - 9) * ( 3+ 9) = -6 * 12 = -72

So, Answer will be A
Hope it helps!

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