If y^2 + 1 – 5y = 0, then what will be the value of y^2+1/y^ 2 ?

RRB NTPC Prelims Model Paper 2 with solutions

Question : 75 of 101

Marks: +1, -0

y^2 + 1 – 5y = 0

, then what will be the value of

y^2+1/y^ 2 ?

Solution:

(1) Dividing each term of

y^2 + 1 – 5y = 0

by y, we get

y^2/Y+ 1/Y- {5y}/Y=0⇒Y+ 1/Y=5

Now,

Y^2+1/Y^2=[Y+1/Y]^2-2

= 5^2 - 2 = 23

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