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Find the value of a1a in terms of ‘m’, if a+1a=manda0.
A). ±m24
B). ±m23
C). ±m29
D). ±m21

Answer
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Hint: We need to use a given expression to find the value of another expression. We have to simplify a given expression and then find the value of the required expression in terms of ‘m’. We need to perform appropriate operations in order to have common terms,
Formula used:
(a+b)2=a2+2ab+b2

Complete step-by-step solution:
Let us note the given equation,
a+1a=m
Let us simplify the above equation,
On squaring both sides we get,
(a+1a)2=m2
On expanding the bracket using formula (a+b)2=a2+2ab+b2 we get,
a2+2+1a2=m2
On subtraction 2 from both sides we get,
a2+1a2=m22 ...................[1]
We need to find the value of a1a
Let us simplify the above equation,
a1a
On squaring both sides we get,
(a1a)2=a22+1a2
On rearranging the terms on R.H.S. we get,
(a1a)2=a2+1a22
Let us put the value from equation [1] , a2+1a2=m22 in above equation,
(a1a)2=m222
On performing subtraction on R.H.S. we get,
(a1a)2=m24
On taking square roots on the both sides we get,
a1a=±m24
This is the required value.
Hence option A) ±m24is correct.

Note: In such questions where both terms have opposite signs, we need to perform operations like squaring, in order to get common terms from two different terms. Then we can substitute the value for a common term to obtain the required equation.