6 si 7 (dau 53 puncte)

6. 2a+3a = a(2+3) = 5a ; 3a+5a = a(3+5) = 8a ; 2x+6x = x(2+6) = 8x ;

9x-2x = x(9-2) = 7x ; 6x+x = x(6+1) = 7x ; 4x-x = x(4-1) = 3x ;

10x-10x = x(10-10) = 0 ; x+x = x(1+1) = 2x ;

7. a) 5x+6x+4x = 15x ; 30x+12x-5x = 37x ; 3x-2x+8x = 9x ; 3x+x+2x = 6x ;

b) 30x+12x-41x = x ; 4x-2x-x = x ; 7x-3x+x = 5x ; 10x-9x-x = 0 ;

c) x+x-2x = 0 ; 8x+10x-2x = 16x ; 7x+x-x = 7x ; x+3x-4x = 0 ;

6)

2a+3a=a*(2+3)=5a

6x+x=x*(6+1)=7x

3a+5a=a*(3+5)=8a

4x-x=x*(4-1)=3x

2x+6x=2x *(1+3)=2x*4=8x

10x-10x=10x(1-1)=10x*0=0

9x-2x=x*(9-2)=x*7=7x

7)

5x+6x+4x=x*(5+6+4)=x*15=15x

30x+12x-5x=x*(30+12-5)=x*37=37x

3x-2x+8x=x*(3-2+8)=x*9=9x

3x+x+2x=x*(3+1+2)=x*6=6x

b)

30x+12x-41x=x*(30+12-41)=x*1=x

4x-2x-x=x*(4-2-1)=x*1=x

7x-3x+x= x*( 7-3+1)=x*5=5x

10x-9x-x=x*( 10-9-1)=x*0=0

c)

x+x-2x=x*(1+1-2)=x*0=0

8x+10x-2x =2x *( 4+5-1)=2x*8=16x

7x+x-x=x*(7+1-1)=x*7=7x

x+3x-4x=x*(1+3-4)=x*0=0