Ex: formula puteri, formule analiza financiara, inmultirea radicalilor exercitii rezolvate
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Sisteme de ecuatii - aranjamente- combinari - exercitiu rezolvat 1

 Ax y = 7Ax y-1
                                                
6Cx y = 5Cx y+1


Astfel =>

 
y ≤ x
y-1 ≤ x
y+1 ≤ x

Ax y = 7Ax y-1 = x! / (x-y)! = 7 * x! / (x-y+1)!

1 / (x-y)! = 7 / (x-y+1)!      * (x– y+1)

x– y+1 = 7
x - y = 6




6Cx y = 5Cx y+1

6 * x! / y! (x - y)! = 5 * x! / (y+1)!(x-y-1)!   

scriem pe  (x - y)!  ca  (x-y-1)! *(x-y)
iar (y+1)! ca y!*(y+1)

*(y+1)                         *(x-y)
6 / y! (x-y-1)!(x - y) = 5 / y!(y+1)(x-y-1)!

eliminam numitorul si =>

6y + 6 = 5x – 5y
5x - 11y = 6


Din ambele ecuatii=>



x - y = 6           /* (-5)
5x - 11y = 6


-5x + 5y = -30          
 5x - 11y = 6

16y = -24

y = -24 / 16

y = -3 / 2  nu € N