Question

a, (x-3)^2-4(x-5)=(4-x)^2

b, 3(x-2)(x+2)=(2x-1)^2-(x-3)^2

c, (x+4)^2-(x-5)^2=5(x-4)

d, x(3+x)^2-1=(x+2)^3

Mong mọi người giúp đỡ!

Answer 1

a) (x-3)²- 4(x-5)= (4-x)²

<=> x²- 6x+ 9- 4x+ 20= 16- 8x+ x²

<=> x²- x²- 6x- 4x+ 8x= 16- 9- 20

<=> -2x = -13

<=> x = \(\frac{13}{2}\)

b) 3(x-2)(x+2) = (2x-1)²-(x-3)²

<=> 3(x²-4) = 4x²- 4x +1 - (x²-6x +9)

<=> 3x² - 12 = 4x² - 4x + 1 - x² +6x - 9

<=> 3x² - 12 = 3x² + 2x - 8

<=> 3x² -3x² - 2x = 12 - 8

<=> -2x = 4

<=> x = -2

c) ( x + 4)²- (x-5)² = 5(x - 4)

<=> x²+ 8x +16 - ( x²-10x +25) = 5x - 20

<=> x²+ 8x +16 - x² +10x -25 = 5x - 20

<=> 18x - 9 - 5x + 20 = 0

<=> 13x + 11 = 0

<=> 13x = -11

<=> x = \(\frac{-11}{13}\)

d) x(3+x)² - 1 = (x+2)³

<=> x( 9 + 6x + x² ) - 1 = x³ + 6x² + 12x + 8

<=> 9x + 6x² + x³ - 1 - x³ - 6x² - 12x - 8 = 0

<=> -3x - 9 = 0

<=> -3x = 9

<=> x = -3