Dacă 14×a-4×b supra 3×a+7×b, calculați a supra b

( 14 × a - 4 × b ) / ( 3 × a + 7 × b ) = 6 / 7

 → produsul miezilor = produsul extremilor

⇒ 7 ×  2 × ( 7 × a - 2 × b ) = 6 × ( 3 × a + 7 × b )      l : 2

7 × ( 7 × a - 2 × b ) = 3 × ( 3 × a + 7 × b )

49 × a - 14 × b = 9 × a + 21 × b

49 × a - 9 × a = 21 × b + 14 × b

40 × a = 35 × b  ⇒   a / b = 35 / 40 = 7 / 8

                   Raspuns:     a / b = 7 / 8

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