If a-\frac{1}{a}=7, then a^{2}+\frac{1}{a^{2}}=?

RRB Group D 17-Sep-2018 Shift 2 Solved Paper

Question : 62 of 100

Marks: +1, -0

a-\;{1}/{a}=7,

then

a^{2}+\;{1}/{a^{2}}=?

Solution:

a-\;{1}/{a}=7, a^{2}+\;{1}/{a^{2}}=?

\;\text " on squaring both sides "\;

(a-\;{1}/{a})^{2}=7^{2}

a^{2}+\;{1}/{a^{2}}-2 ⋅ a ⋅ \;{1}/{a}=49

a^{2}+\;{1}/{a^{2}}-2=49

a^{2}+\;{1}/{a^{2}}=51

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