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b is the answer
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a=√5 -2
ab is rational
hence b is the rationalising factor of a, i.e. multiplying it with a gives a rational number
the rationalising factor of a is √5 +2
as (√5 -2)*(√5 +2)=(√5)^2-(2)^2 =1 (a rational) [a^2-b^2=(a+b)(a-b)]
hence b=√5 +2 (answer)
{Read below only if u understood the above}
these kind of surds which are negative to each other and whose product is rational are called conjugate surds
eg √5-2 and √5+2
eg √2+5 and √2 -5
etc..
these are rationalising factor of each other.
thank u hope I have helped u!
ab is rational
hence b is the rationalising factor of a, i.e. multiplying it with a gives a rational number
the rationalising factor of a is √5 +2
as (√5 -2)*(√5 +2)=(√5)^2-(2)^2 =1 (a rational) [a^2-b^2=(a+b)(a-b)]
hence b=√5 +2 (answer)
{Read below only if u understood the above}
these kind of surds which are negative to each other and whose product is rational are called conjugate surds
eg √5-2 and √5+2
eg √2+5 and √2 -5
etc..
these are rationalising factor of each other.
thank u hope I have helped u!
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