If a+b=9 and a²-b²=27 find the value of ab?
vishagh:
i guess there is a small error in question, it should be a²+b²=27
There is a property in which (a^2 - b^2)= (a-b)(a+b)
but then ab will get canceled.hw will we find its value
Put value of a+b and calculate a-b and hence solve the two equations and you will get values of a&b then multiply them..18 will be the answer
I have tried to solve the question
Hope it will help you..
Answers
Answered by
9
a+b=9
squaring both sides we get
(a+b)²=9²
a²+b²+2ab=81.................................................(1)
given a²+b²=27
substituting value of a²+b²=27 in ....(1)
we get
⇒27+2ab=81
2ab=54
ab=54/2=27
∴value of ab=27
Hope it helped...!!!
squaring both sides we get
(a+b)²=9²
a²+b²+2ab=81.................................................(1)
given a²+b²=27
substituting value of a²+b²=27 in ....(1)
we get
⇒27+2ab=81
2ab=54
ab=54/2=27
∴value of ab=27
Hope it helped...!!!
Answered by
4
{a square + b square}
(a^2 + b^2)= (a-b)(a+b)= 27--------(1)
Also given that a+b = 9---------(2)
Putting (2) in (1)
We get (a-b)= 27/9 = 3-------(3)
Now add equations (2) and (3)
2a = 12
a=6
Put the value of a and get the value of b= 3 therefore ab= 6*3= 18.....
(a^2 + b^2)= (a-b)(a+b)= 27--------(1)
Also given that a+b = 9---------(2)
Putting (2) in (1)
We get (a-b)= 27/9 = 3-------(3)
Now add equations (2) and (3)
2a = 12
a=6
Put the value of a and get the value of b= 3 therefore ab= 6*3= 18.....
If the question has no error thn i guess ur answer is ryt... :)
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