Question

21. Determinati numarul real m , stiind ca -3 este solutie a urmatoarelor ecuatii cu necunoscuta x :

a) 4m-1=5x+18
b) 6x-7m=3x+5
c) 2(x+2m) = mx+1
d) x-13m=6(mx-3)

Answer 1

a)

4m-1=5x+18

4m-1=5·(-3)+18

4m-1=-15+18

4m-1=3

4m=3+1

4m=4

m=4:4

m=1

b)

6x-7m=3x+5

6·(-3)-7m=3·(-3)+5

-18-7m=-9+5

-18-7m=-4

-7m=-4+18

-7m=14

m=14:(-7)

m=-2

c)

2(x+2m) = mx+1

2(-3+2m) = m·(-3)+1

-6+4m=-3m+1

4m=-3m+1+6

4m=-3m+7

4m+3m=7

7m=7

m=1

d)

x-13m=6(mx-3)

-3-13m=6[m·(-3)-3]

-3-13m=6(-3m-3)

-3-13m=-18m-18

-13m=-18m-18+3

-13m=-18m-15

-13m+18m=-15

5m=-15

m=-15:5

m=-3