a) Ta có |7x-1-(5-x+2[tex]x^2[/tex] )|
= [tex]\left[\begin{7x-1-(5-x+2[tex]x^2[/tex]}\\{-7x+1+(5-x+2[tex]x^2[/tex])}[/tex]
=> A = [tex]\left[\begin{2[tex]x^2[/tex]+7x-1-(5-x+2[tex]x^2[/tex])}\\{2[tex]x^2[/tex]-7x+1+(5-x+2[tex]x^2[/tex])}[/tex]
=> A = [tex]\left[\begin{2[tex]x^2[/tex]+7x-1-5+x-2[tex]x^2[/tex]}\\{2[tex]x^2[/tex]-7x+1+5-x+2[tex]x^2[/tex]}[/tex]
=> A = [tex]\left[\begin{(2[tex]x^2[/tex]-2[tex]x^2[/tex])+(7x+x)+(-1-5)}\\{(2[tex]x^2[/tex]+2[tex]x^2[/tex]+(-7x-x)+(1+5)[/tex]
=> A = [tex]\left[\begin{8x-6}\\{4[tex]x^2[/tex]-8x+6}[/tex]
b) Nếu A = 8x-6
=> 8x - 6 = 2
=> 8x = 2 + 6
=> 8x = 8
=> x = 8 : 8
=> x = 1
- Nếu A = 4[tex]x^2[/tex] - 8x + 6
=> 4[tex]x^2[/tex] - 8x + 6 = 2
=> 4[tex]x^2[/tex] - 8x = 2 - 6
=> 4[tex]x^2[/tex] - 8x = -4