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 4 of 11.
Krishna said:
1 decade ago
a^2+b^2=(a-b)(a-b)+2ab. Now putting the value of (a-b)we get that 9+2ab=29, 2ab=20, ab=10.
Prasad said:
1 decade ago
(a-b)^2 = a^2+b^2-2ab.
Then 2ab = (a^2+b^2)-(a-b)^2.
2ab = 29-(3)^2.
2ab = 20.
ab = 10.
Then 2ab = (a^2+b^2)-(a-b)^2.
2ab = 29-(3)^2.
2ab = 20.
ab = 10.
Lokmani said:
1 decade ago
a-b=3
a^2+b^2=29
(a-b)^2=a^2+b^2-2ab
(3)^2=29-2ab
9=29-2ab
2ab=29-9
2ab=20
ab=20/2
ab=10
a^2+b^2=29
(a-b)^2=a^2+b^2-2ab
(3)^2=29-2ab
9=29-2ab
2ab=29-9
2ab=20
ab=20/2
ab=10
Vishnu dilip said:
1 decade ago
Easy method
Given
a - b = 3 and a*a - b*b = 3,
So,
a = 5 and b= 2,
So,
ab = 5*2 = 10
Given
a - b = 3 and a*a - b*b = 3,
So,
a = 5 and b= 2,
So,
ab = 5*2 = 10
Satish said:
1 decade ago
Actually (a-b)^2 = a^2 - 2ab + b^2 substitute in above formula we can get the answer.
Sandilya said:
9 years ago
Yes @Harsh Singh.
(a+b)2 = (a-b)2+4ab,
(a+b)2 = 256,
a+b = +-16.
+-16 is the answer.
(a+b)2 = (a-b)2+4ab,
(a+b)2 = 256,
a+b = +-16.
+-16 is the answer.
Abid said:
8 years ago
Please solve this problem.
If √a + √b- √c = 0 Then find (a+b-c)^2.
If √a + √b- √c = 0 Then find (a+b-c)^2.
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)
Farman said:
8 years ago
Let's look it if a2+b2=25 and a-b=3 ab=?
25-(3)^2=16 then 16/2 =8.
25-(3)^2=16 then 16/2 =8.
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