Question

a) 25x² -9 =0

b) (x+4)² - (x+1)(x-1) =16

c) (2x-1)² + (x+3)² -5(x+7)(x-7) =0

Answer 1

a/

=> 25x² = 9

=> (5x)² = 3²

=> 5x = 3 

=> x = 3/5

Answer 2

b/ 

=> x² + 8x + 16 - x² - 1 = 16

=> 8x + 15 = 16

=> 8x = 1

=> x = 1/8

Answer 3

c/ 

=> 2x² - 4x + 1 + x² + 6x + 9 - 5x² - 245 = 0

=> - 2x² + 2x - 235 = 0

=> ( - 2x²  + 2(-2)x.(-1/2)+ 1/4)-1/4 = 235

=> (-2x + 1/4)² - 1/4 = 235

=>    :(          rối wa ko pit sai ko nua

Answer 4

c/ 

=> 2x² - 4x + 1 + x² + 6x + 9 - 5x² - 245 = 0

=> - 2x² + 2x - 235 = 0

=> ( - 2x²  + 2(-2)x.(-1/2)+ 1/4)-1/4 = 235

=> (-2x + 1/4)² - 1/4 = 235

=>