Question

Tìm x biết :

a) x^2 - 2x - 3 = 0                                                                                                      b) 2x^2 + 5x - 3 = 0

Answer 1

a/=> x² - 3x + x - 3 = 0 

=> x(x-3) + (x-3) = 0 

=> (x+1)(x-3) = 0

=> x + 1 = 0 => x = -1

hoặc x - 3 = 0 => x = 3

b/ => 2x² - x + 6x - 3 = 0 

=> x (2x-1) + 3 (2x-1) = 0 

=> (x+3) (2x-1) = 0

=> x + 3 = 0 => x = -3

hoặc 2x - 1 = 0 => 2x = 1 => x = 1/2

Answer 2

 

a) x^2 - 2x - 3 = 0

<=>x²+x-3x-3=0

<=>x.(x+1)-3.(x+1)=0

<=>(x+1)(x-3)=0

<=>x+1=0 hoặc x-3=0

<=>x=-1 hoặc x=3                                                                                                   

b) 2x^2 + 5x - 3 = 0

<=>2x²-x+6x-3=0

<=>x.(2x-1)+3.(2x-1)=0

<=>(2x-1)(x+3)=0

<=>2x-1=0 hoặc x+3=0

<=>x=1/2 hoặc x=-3

 

Answer 3

x=1/2