Question

Dacă x+y=8 și y+2z=35
a) 5x+13y+16z
b) 3y-2x+10z
c)7x+10y+6z
d)4. (2z+y)+3x+3y

Answer 1

x + y = 8   si   y + 2 z = 35

a)   5 x + 13 y + 16 z =  320

= 5 x +( 5 y + 8 y )+ 16 z =

=  5 · ( x + y ) + 8 · ( y + 2 z ) =

= 5 × 8 + 8 × 35 =

=  40 + 280 =

= 320

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b)   3 y - 2 x + 10 z = 159

= 5 × ( y + 2 z ) - 2 × ( x + y ) =

= 5 × 35 - 2 × 8 =

= 175 - 16 =

= 159

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c)   7 x + 10 y + 6 z = 161

= 7 x + ( 7 y + 3 y ) + 6 z =

= 7 × ( x + y ) + 3 × ( y + 2 z ) =

= 7 × 8 + 3 × 35 =

= 56 + 105 =

= 161

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d)  4 × ( 2 z + y ) + 3 x + 3 y = 164

= 4 × 35 + 3 × ( x + y ) =

= 140 + 3 × 8 =

= 140 + 24

= 164