Let p and q be two real numbers such that p+q | vedclass

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Question

$p + q =3 \quad p ^{4}+ q ^{4}=369$

$\left(\frac{1}{p}+\frac{1}{q}\right)^{-2}$

$(p+q)^{2}=9$

$p ^{2}+ q ^{2}=9-2 pq$

$\frac{1}{\left(\fra

Vedclass · Accepted Answer

$4$

Vedclass · Answer

$p + q =3 \quad p ^{4}+ q ^{4}=369$

$\left(\frac{1}{p}+\frac{1}{q}ight)^{-2}$

$(p+q)^{2}=9$

$p ^{2}+ q ^{2}=9-2 pq$

$\frac{1}{\left(\frac{1}{p}+\frac{1}{q}ight)^{2}}=\frac{(q p)^{2}}{(q+p)^{2}}=\frac{(q p)^{2}}{9}$

$p ^{4}+ q ^{4}=\left( p ^{2}+ q ^{2}ight)^{2}-2 p ^{2} q ^{2}$

$369=(9-2 p q)^{2}-2(p q)^{2}$

$369=81+4 p ^{2} q ^{2}-36 pq -2 p ^{2} q ^{2}$

$288=2 p ^{2} q ^{2}-36 pq$

$144= p ^{2} q ^{2}-18 pq$

$( pq )^{2}-2 	imes 9 	imes pq +9^{2}=144+9^{2}$

$(p q-9)^{2}=225$

$p q-9=\pm 15$

$p q=\pm 15+9$

$p q=24,-6$

($24$ is rejected because $p ^{2}+ q ^{2}=9-2 pq$ is negative)

$\frac{(q p)^{2}}{9}=\frac{16 	imes 16}{9}=4$

Let $p$ and $q$ be two real numbers such that $p+q=$ 3 and $p^{4}+q^{4}=369$. Then $\left(\frac{1}{p}+\frac{1}{q}\right)^{-2}$ is equal to

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