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DiaconuDenise
a fost răspuns

Daca x + 2y=17 si y - 3z =4, calculati :

a) x + 3y - 3z =
b) 2x + 5y -3z =
c) ( 3x + 6y )+ ( 2y - 6z )
d) ( 2y + 4y ) x ( x +4y - 6z )

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Răspuns :

Cocirmariadenis

x + 2 y = 17   si   y - 3 z = 4

a)    x  + 3 y - 3 z = ( x + 2 y ) + ( y - 3 z ) = 17 + 4 = 21

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b)   2 x + 5 y - 3 z = 38

= 2 × ( x + 2 y ) + ( y - 3 z ) =

= 2 × 17 + 4 =

= 34 + 4 =

= 38

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c)    ( 3 x + 6 y ) + ( 2 y - 6 z ) =

= 3 ( x + 2 y ) + 2 ( y - 2 z ) =

= 3 × 17 + 2 × 4 =

= 51 + 8 =

= 59

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d)   ( 2 x + 4 y ) × ( x + 4 y - 6 z ) = 850

= 2 × ( x + 2 y ) × [ ( x + 2 y )  + 2 ( y - 3 z ) ] =

= ( 2 × 17 ) × ( 17 + 2 × 4 ) =

= 34 × 25 =

= 850

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