Aptitude - Square Root and Cube Root - Discussion
Discussion Forum : Square Root and Cube Root - General Questions (Q.No. 6)
6.
If a = 0.1039, then the value of 4a2 - 4a + 1 + 3a is:
Answer: Option
Explanation:
4a2 - 4a + 1 + 3a = (1)2 + (2a)2 - 2 x 1 x 2a + 3a
= (1 - 2a)2 + 3a
= (1 - 2a) + 3a
= (1 + a)
= (1 + 0.1039)
= 1.1039
Discussion:
71 comments Page 3 of 8.
Phani said:
10 years ago
Why should we take (1-2a) and the given is 4a^2 -4a+1 we can also take 2a-1.
Gupta said:
10 years ago
How is it 1-2a? It should be 2a-1.
Renga said:
9 years ago
2a - 1 + 3a = 5a - 1.
= 5(0.1039) - 1 = -0.4805.
Can you please explain, what is (1 - 2a)?
= 5(0.1039) - 1 = -0.4805.
Can you please explain, what is (1 - 2a)?
Zareena said:
9 years ago
(1 - 2a)2 is wrong because if you expand it give 4a^2 + 4a + 1 which is not matching with the question.
So, - 0.4805 is the right answer.
So, - 0.4805 is the right answer.
Bhavuk Singh said:
9 years ago
Given , a = 0.1039
2a - 1= 2(0.1039) - 1 = - .7922.
The square root of a negative number is not a real number. Hence, we use (1 - 2a).
2a - 1= 2(0.1039) - 1 = - .7922.
The square root of a negative number is not a real number. Hence, we use (1 - 2a).
Harshit said:
9 years ago
Given that a = 0.1039; a<<1; this implies a^2<<<1 and hence it can be ignored int the expression.
So, the value should be approximately equal to 1 - a = 0.8961. The exact value is 0.9393 is also nearly equal to it.
But the option does not contain any matching value. So why should not we consider this question ambiguous?
So, the value should be approximately equal to 1 - a = 0.8961. The exact value is 0.9393 is also nearly equal to it.
But the option does not contain any matching value. So why should not we consider this question ambiguous?
Jaju said:
9 years ago
Hi @Bhavuk Singh.
How told you to take the square root of - .7922?
Actually, when you take the square root of (2a-1) ^2 it will give you two result either 2a-1 else 1-2a.
You can choose any of the two and yes, two results are possible here. Keeping in mind options given you have to select any one of twos. I think this is clear now?
How told you to take the square root of - .7922?
Actually, when you take the square root of (2a-1) ^2 it will give you two result either 2a-1 else 1-2a.
You can choose any of the two and yes, two results are possible here. Keeping in mind options given you have to select any one of twos. I think this is clear now?
Rahul said:
9 years ago
I do not understand the explanation. Please clarify me.
Divi said:
9 years ago
4a^2 - 4a + 1 = (2a - 1)^2
Then square and root cancelld.
2a - 1 + 3a = 5a - 1.
5(0.1039) - 1 = 0.5195 - 1 = 0.4805 is this correct? I it is wrong, anyone explain me.
Then square and root cancelld.
2a - 1 + 3a = 5a - 1.
5(0.1039) - 1 = 0.5195 - 1 = 0.4805 is this correct? I it is wrong, anyone explain me.
Sandeep said:
9 years ago
@DIVI.
Answer will be in -ve if you subtracting 0.5195 - 1.
Answer will be in -ve if you subtracting 0.5195 - 1.
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