Question

Find.

If (3)x+7= 81 and (81)x-y =3 find x&y.

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Answer 1

Answer:

81x=(34)x=(3x)4.

u=3x

⟹3x+y=81

⟹u+y=81

⟹y=81−u.

u=3x

⟹81x−y=3

⟹(3x)4−y=3

⟹u4−y=3

⟹y=u4−3.

y=y

⟹81−u=u4−3

⟹u4+u−84=0

⟹u=3

⟹3x=31

⟹x=1.

31+y=81

⟹y=81−3

⟹y=78.

∴x=1, y=78.

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