b) 1/ x + 1 + 2/ x + 2 = 5/6
Giải thích
b) 1x+1+2x+2=56 x≠−1x≠−2⇔x+2+2(x+1)(x+1)(x+2)=56
⇔3x+4x2+3x+2=56⇒18x+24=5x2+15x+10⇔5x2−3x−14=0⇔x=2x=−75 (thoa)S=2;−75
b) 1x+1+2x+2=56 x≠−1x≠−2⇔x+2+2(x+1)(x+1)(x+2)=56
⇔3x+4x2+3x+2=56⇒18x+24=5x2+15x+10⇔5x2−3x−14=0⇔x=2x=−75 (thoa)S=2;−75