Răspuns :

Răspuns:

a)51

b)72

c)9

d)111

Explicație pas cu pas:

a)a+b=21=>a=21-b

b+c=30=>c=30-b

a+2xb+c=21-b+2xb+30-b=51

b)2xa+3xb+c=42-2xb+2xb+30-b=72

c)c-a=30-b-21+b=9

d)a=4xb+3xc=21-b+4xb+90-3b=111

Cocirmariadenisid

Răspuns:

Explicație pas cu pas:

a + b      = 21    

     b + c = 30

___________ adun relatiile

a + 2 × b + c = 21 + 30

a + 2 × b + c = 51

__________________

b)

( b + c ) - ( a + b) = 30 - 21

b + c - a - b = 9

c - a = 9

_____________________

c)

2 × a + 3 × b + c = 72

= 2 × a + 2 × b + b + c =

= 2 × ( a + b ) + ( b + c) =

= 2 × 21 + 30 =

= 42 + 30 =

= 72

___________________

d)

a + 4 × b + 3 × c = 111

= a + b + 3 × b + 3 × c =

= ( a + b) + 3 × ( b + c ) =

= 21 + 3 × 30 =

= 21 + 90 =

= 111

ID Alte intrebari