Đáp án+Giải thích các bước giải:
a. (a-2) (b + 5) = 13
nếu a-2=13=>a=15;b+5=1=>b=-4
nếu a-2=1=>a=3;b+5=13=>b=8
nếu a-2=-13=>a=-12;b+5=-1=>b=-6
nếu a-2=-1=>a=1;b+5=-13=>b=-18
b. a(b-4) +4(b-4) =5
(a+4)(b-4)=5
nếu a+4=5=>a=1;b-4=1=>b=5
nếu a+4=1=>a=-3;b-4=5=>b=9
nếu a+4=-5=>a=-9;b-4=-1=>b=3
nếu a+4=-1=>a=-5;b-4=-5=>b=-1
c. (ab+3b) + (2a+6) =-3
b(a+3)+2(a+3)=-3
(b+2)(a+3)=-3
nếu a+3=-3=>a=-6;b+2=1=>b=-1
nếu a+3=1=>a=-2;b+2=-3=>b=-5
nếu a+3=-1=>a=-4;b+2=3=>b=1
nếu a+3=3=>a=0;b+2=-1=>b=-3
d. ab+3a+2b=7
a.(b+3)+2b+6=7+6=13
a.(b+3)+(b+3).2=13
(a+2).(b+3)=13
nếu a+2=-13=>a=-15;b+3=-1=>b=-4
nếu a+2=1=>a=-3;b+3=13=>b=10
nếu a+2=-1=>a=-3;b+3=-13=>b=-16
nếu a+2=-13=>a=-15;b+3=-1=>b=-4
