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.
Sachin Kumar said:
8 years ago
@Gween.
a + b = 4
means a=4-b.
Put this value in the equation
5= 2(4-b)+3b,
5= 8-2b+3b,
5-8 = -2b+3b,
-3= b.
Put the value of b in the equation and u will get the value of a.
Thats it!
a + b = 4
means a=4-b.
Put this value in the equation
5= 2(4-b)+3b,
5= 8-2b+3b,
5-8 = -2b+3b,
-3= b.
Put the value of b in the equation and u will get the value of a.
Thats it!
MANOJ K P said:
1 decade ago
VERY SIMPLE.
A-B = 3.
SQUARE IT BOTH SIDE.
(A-B) ^2 = (3*3).
A^2+B^2-2AB = 9.
2AB = A^2+B^2-9.
WE HAVE A^2+B^2 = 29 APPLY THIS.
2AB = 29-9.
2AB = 20.
AB = 20/2.
AB = 10.
A-B = 3.
SQUARE IT BOTH SIDE.
(A-B) ^2 = (3*3).
A^2+B^2-2AB = 9.
2AB = A^2+B^2-9.
WE HAVE A^2+B^2 = 29 APPLY THIS.
2AB = 29-9.
2AB = 20.
AB = 20/2.
AB = 10.
Neeraj Kashyap said:
9 years ago
Please solve the following with explanation:
1. (a + b) (a - b) + (2a + b) (2a - 3b).
2. (x - y)(2x + y) - (x + y)(2x - y).
3. (x + 6){5x - 3(x - 2)}
4. 7x - 3{x - 2x(x - 4)}
1. (a + b) (a - b) + (2a + b) (2a - 3b).
2. (x - y)(2x + y) - (x + y)(2x - y).
3. (x + 6){5x - 3(x - 2)}
4. 7x - 3{x - 2x(x - 4)}
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)
Bonjor said:
9 years ago
I would be grateful if anyone answers this question.
If a-b=4 and ab=60 then find the value of a+b.
I found that the answer is + or - 16 what is + or -? Please tell me.
If a-b=4 and ab=60 then find the value of a+b.
I found that the answer is + or - 16 what is + or -? Please tell me.
Prince said:
7 years ago
We can write a^2+b^2=(a-b)^2+2ab.
When we solve (a-b)^2+2ab we will get a^2+b^2.
Now put the value of (a-b) and a^2+b^2 in the equation a^2+b^2=(a-b)^2+2ab.
Ans is - 10.
When we solve (a-b)^2+2ab we will get a^2+b^2.
Now put the value of (a-b) and a^2+b^2 in the equation a^2+b^2=(a-b)^2+2ab.
Ans is - 10.
Sachin Kumar said:
8 years ago
If a^2+b^2 = (a+b)^2.
And (a+b)^2 = a^2+b^2+2ab.
It means a^2+b^2 = a^2+b^2+2ab.
But How Could it Possible,
Please somebody tell me what actually is it?
And (a+b)^2 = a^2+b^2+2ab.
It means a^2+b^2 = a^2+b^2+2ab.
But How Could it Possible,
Please somebody tell me what actually is it?
Myself said:
1 decade ago
(a-b)2= a2+b2-2ab..................{eq 1}
it is given that:(a-b)=3,a2+b2=29.
so put it in {eq 1},we get:
3*3=29-2ab.
9=29-2ab.
2ab=29-9
2ab=20
ab=10.
it is given that:(a-b)=3,a2+b2=29.
so put it in {eq 1},we get:
3*3=29-2ab.
9=29-2ab.
2ab=29-9
2ab=20
ab=10.
Sonali said:
9 years ago
a-b = 3, a2+b2=29, ab =?
(a-b)2 = a2+b2-2ab
2ab = (a2+b2)-(a-b)2
ab = 29-9/2
= 20/2 = 10 Ans.
(a-b)2 = a2+b2-2ab
2ab = (a2+b2)-(a-b)2
ab = 29-9/2
= 20/2 = 10 Ans.
Kavi said:
1 decade ago
a-b=3 and a2+b2=29
b=a-3 sub in above equ,
a2+(a-3)2=29
a2+a2-6a+9=29
a2-3a-10=0
a=5 or -2
let we taken a=5
5^2+b2=29
25+b2=29
b=2
ab=(5)(2)
ab=10
b=a-3 sub in above equ,
a2+(a-3)2=29
a2+a2-6a+9=29
a2-3a-10=0
a=5 or -2
let we taken a=5
5^2+b2=29
25+b2=29
b=2
ab=(5)(2)
ab=10
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