Aptitude - Simplification - Discussion
Discussion Forum : Simplification - General Questions (Q.No. 4)
4.
If a - b = 3 and a2 + b2 = 29, find the value of ab.
Answer: Option
Explanation:
2ab = (a2 + b2) - (a - b)2
= 29 - 9 = 20
ab = 10.
Discussion:
107 comments Page 1 of 11.
Btisso said:
2 years ago
How 3 has come? Anyone, please explain me.
(8)
GyaniAdmy said:
2 years ago
a-b = 3.
a^2+b^2 = 29.
Let's Get The Answer In (a-b)^2 Formula/Format
(a-b)^2=a^2+b^2-2ab
=>3^2 = 29 - 2ab
=>9 = 29 - 2ab
=>2ab = 29 - 9
=>2ab = 20.
Therefore, ab=10.
Wasn't It Easy?
a^2+b^2 = 29.
Let's Get The Answer In (a-b)^2 Formula/Format
(a-b)^2=a^2+b^2-2ab
=>3^2 = 29 - 2ab
=>9 = 29 - 2ab
=>2ab = 29 - 9
=>2ab = 20.
Therefore, ab=10.
Wasn't It Easy?
(94)
Deepika said:
3 years ago
a-b = 3
a^2 + b^2 = 29.
To find ab;
Let's consider A as 5 and B as 2.
a - b = 3,
5 - 2 = 3,
a^2 = 25,
b^2 = 4.
ab = 5 * 2 = 10.
a^2 + b^2 = 29.
To find ab;
Let's consider A as 5 and B as 2.
a - b = 3,
5 - 2 = 3,
a^2 = 25,
b^2 = 4.
ab = 5 * 2 = 10.
(29)
Heyrobin said:
3 years ago
It's easy.
Use the formula!
(a+b)2 = a2 + b2 + 2ab.
(a-b)2 = a2+b2 - 2ab.
I am choosing (a-b)2 formula as that is in my question a-b = 3.
(a-b)2 = (a2+b2) - 2ab.
(3)2 = (29) - 2ab.
9 = 29 - 2ab.
2ab= 29-9.
ab= 20/2.
ans = 10.
Use the formula!
(a+b)2 = a2 + b2 + 2ab.
(a-b)2 = a2+b2 - 2ab.
I am choosing (a-b)2 formula as that is in my question a-b = 3.
(a-b)2 = (a2+b2) - 2ab.
(3)2 = (29) - 2ab.
9 = 29 - 2ab.
2ab= 29-9.
ab= 20/2.
ans = 10.
(28)
Tulasi said:
3 years ago
a-b=3 ----> (i)
a^2+b^2=29 ----> (ii).
Eqn(i) squaring on both sides
(a-b)^2 = 3^2.
a^2+b^2-2ab=9.
a^2+b^2=9+2ab ----> (iii)
substitute eqn(iii) in eqn(ii).
a^2+b^ 2= 29,
9+2ab = 29,
2ab = 29-9,
2ab = 20,
ab = 10.
a^2+b^2=29 ----> (ii).
Eqn(i) squaring on both sides
(a-b)^2 = 3^2.
a^2+b^2-2ab=9.
a^2+b^2=9+2ab ----> (iii)
substitute eqn(iii) in eqn(ii).
a^2+b^ 2= 29,
9+2ab = 29,
2ab = 29-9,
2ab = 20,
ab = 10.
(8)
Avi said:
4 years ago
Thanks @Satish.
(2)
Varshith said:
5 years ago
Thanks @Janu.
(2)
Sunil said:
5 years ago
Simply tack, a-b=3 n square on both side .
A square + b square - 2AB=3 square----------> (1).
29-2AB=9 HENCE 2AB=29-9> 2AB=20 SO AB=10.
A square + b square - 2AB=3 square----------> (1).
29-2AB=9 HENCE 2AB=29-9> 2AB=20 SO AB=10.
(1)
Sai said:
5 years ago
Can anyone explain this once again clearly?
(1)
Alex said:
6 years ago
Thanks for explaining @Dharmender Meena.
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