Question

Resolve : 5x²-45=0.......3x²-5x=0 ....,.... X²-81=0

Answer 1

5 x²  -  45 = 0
5 x(x - 9) = 0
5 x = 0
x = 0/5
x = 0
x  -  9 = 0
x = 9
S = {0 ; 9}

3 x²  -  5 x = 0
x(3 x - 5 ) = 0
x = 0
3 x - 5 = 0
3 x = 5
x = 5/3
S = {0 ; 5/3}

x²  -  81 = 0
x² = + ou - √81
x = + ou -  9
S = {+9 ; - 9}