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Determinati nr natural astfel incat urmatoarele fractii sa fie egale cu fractia 3 supra 4:
a) n supra 16
b) n+1 supra 8
c) 6 supra n-1
d) 30 supra 2n
e) 3 supra 7n-10
f) 12 supra 3n+4
g) n+2 supra n+3
h) 60 supra n+7
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Răspuns :

a) n/16 = 3/4 => 4n = 16 * 3 => 4n = 48 => n = 12

b) (n+1)/8 = 3/4 => 4n + 4 = 24 => 4n = 20 => n = 5

c) 6/(n-1) = 3/4 => 24 = 3n - 3 => 3n = 27 => n = 9

d)  30/2n = 3/4 => 120 = 6n => n = 120/6 => n = 20

e) 3/(7n-10) = 3/4 => 12 = 21n - 30 => 21n = 42 => n = 2

f) 12/(3n+4) = 3/4 => 48 = 9n + 12=> 9n = 36 => n = 4

g) (n+2)/(n+3) = 3/4 => 4n + 8 = 3n + 9 => n = 1

h) 60/(n+7) = 3/4 => 240 = 3n + 21 => 3n = 219 => n = 73