Question

4x2-1 = ( 2x+1) ( 3x-5)

Answer 1

4x² - 1 = (2x + 1)(3x - 5)

<=> 6x² - 10x + 3x - 5 - 4x² + 1 = 0

<=> 2x² - 7x - 4 = 0

<=> 2x² - 8x + x - 4 = 0

<=> 2x(x - 4) + (x - 4) = 0

<=> (x - 4)(2x + 1) = 0

<=> \(\left[{}\begin{matrix}2x+1=0\\x-4=0\end{matrix}\right.\)

<=> \(\left[{}\begin{matrix}x=-\dfrac{1}{2}\\x=4\end{matrix}\right.\)

Vậy S = {- 0,5 : 4}

Answer 2

(2x+1)(2x-1)=(2x+1)(3x-5)

<=>(2x-1)(2x+1)-(2x-1)(3x-5)=0

<=>(2x+1)(2x-1-3x+5)=0

<=>(2x+1)(4-x)=0

=> (2x+1)=0 hoac (4-x)=0

+, 2x+1=0 <=>2x=-1 <=>x=\(\dfrac{-1}{2}\)

+, 4-x=0 <=>x=4

vay x thuộc tap hợp \(\dfrac{-1}{2};4\)