A
a01688799150
câu 1: (x+1)(x+2)(x+4)(x+5)=40
<=> (x^2+6x+5)(x^2+6x+8)-40=0
<=> (x^2+6x+6,5x)^2-42,25=0
<=> (x^2+6x+13)(x^2+6x)=0
<=> x(x+6)=0
<=> x=0 hoặc x=-6
<=> (x^2+6x+5)(x^2+6x+8)-40=0
<=> (x^2+6x+6,5x)^2-42,25=0
<=> (x^2+6x+13)(x^2+6x)=0
<=> x(x+6)=0
<=> x=0 hoặc x=-6