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# If (a + b)^2 = 36, and ab = 4, then a^2 + b^2 =

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Math Expert
Joined: 02 Sep 2009
Posts: 58335
If (a + b)^2 = 36, and ab = 4, then a^2 + b^2 =  [#permalink]

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22 Jan 2019, 00:54
00:00

Difficulty:

15% (low)

Question Stats:

91% (00:56) correct 9% (00:45) wrong based on 16 sessions

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If $$(a + b)^2 = 36$$, and $$ab = 4$$, then $$a^2 + b^2 =$$

A 3
B 6
C 9
D 28
E 32

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Joined: 31 Oct 2013
Posts: 1475
Concentration: Accounting, Finance
GPA: 3.68
WE: Analyst (Accounting)
Re: If (a + b)^2 = 36, and ab = 4, then a^2 + b^2 =  [#permalink]

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22 Jan 2019, 00:59
Bunuel wrote:
If $$(a + b)^2 = 36$$, and $$ab = 4$$, then $$a^2 + b^2 =$$

A 3
B 6
C 9
D 28
E 32

$$a^2 + b^2$$

=(a + b)^2 -2ab

= 36 - 2.4

=28.

Intern
Joined: 24 Jun 2014
Posts: 5
Re: If (a + b)^2 = 36, and ab = 4, then a^2 + b^2 =  [#permalink]

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22 Jan 2019, 01:07
Using (a+b)^2 = a^2 + 2ab + b^2

36 = a^2 + 2*4 + b^2

Hence a^2 + b^2 = 36 - 8 = 28

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Re: If (a + b)^2 = 36, and ab = 4, then a^2 + b^2 =   [#permalink] 22 Jan 2019, 01:07
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