Question

Tìm x, biết rằng a x(x-3)+x²-9=0 B)x²-7x=0

Answer 1

a) x(x - 3) + x² - 9 = 0

x(x - 3) + (x - 3)(x + 3) = 0

(x - 3)(x + x + 3) = 0

(x - 3)(2x + 3) = 0

x - 3 = 0 hoặc 2x + 3 = 0

*) x - 3 = 0

x = 3

*) 2x + 3 = 0

2x = -3

x = -3/2

Vậy x = -3/2; x = 3

b) x² - 7x = 0

x(x - 7) = 0

x = 0 hoặc x - 7 = 0

*) x - 7 = 0

x = 7

Vậy x = 0; x = 7

Answer 2

tìm x 

a,             x ( x -3) + x² - 9 = 0

   x ( x - 3) + ( x - 3)( x + 3) = 0

             ( x - 3) ( x + x + 3) = 0

                     ( x -3)(2x + 3) =0

                     \(\left[{}\begin{matrix}x-3=0\\2x+3=0\end{matrix}\right.\) 

                      \(\left[{}\begin{matrix}x=3\\x=-\dfrac{3}{2}\end{matrix}\right.\)