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 2 of 11.
Laxmi said:
7 years ago
What will be the answer, if a+b=5, a^2 + b^2 =30, Find b.
Anyone olve it.
Anyone olve it.
(1)
Saritha said:
7 years ago
it is given that (a-b)=3 and a^2+b^2=29.
So,
(a-b)^2=a^2+b^2-2ab.
{substitute a-b=3 and a^2+b^2=29}
=>3^2=29-2ab,
=>2ab=20,
=> ab=10.
So,
(a-b)^2=a^2+b^2-2ab.
{substitute a-b=3 and a^2+b^2=29}
=>3^2=29-2ab,
=>2ab=20,
=> ab=10.
(1)
Jan said:
7 years ago
(a-b)^2 = a^2+b^2-2ab.
(3)^2 = 29-2ab,
9 = 29-2ab,
9-29 = -2ab,
-20 = -2ab,
10 = ab.
(3)^2 = 29-2ab,
9 = 29-2ab,
9-29 = -2ab,
-20 = -2ab,
10 = ab.
(1)
Jan said:
7 years ago
(a-b)^2 = a^2+b^2-2ab.
(3)^2 = 29-2ab,
9 = 29-2ab,
9-29 = -2ab,
-20 = -2ab,
10 = ab.
(3)^2 = 29-2ab,
9 = 29-2ab,
9-29 = -2ab,
-20 = -2ab,
10 = ab.
(1)
Alex said:
6 years ago
Thanks for explaining @Dharmender Meena.
(1)
Sai said:
6 years ago
Can anyone explain this once again clearly?
(1)
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)
Satish said:
1 decade ago
Actually (a-b)^2 = a^2 - 2ab + b^2 substitute in above formula we can get the answer.
Kumar said:
1 decade ago
It's correct.
Sharmila said:
1 decade ago
@Satish is correct this is easy.
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