Đáp án:
Giải thích các bước giải:
6. a. |a|=2⇔a=±2
b. |a|=2⇔a=±2
c. |a|=-3⇒vô nghiệm
d. |a|=|-5|=5⇔a=±5
e. -11|a|=-22⇔|a|=2⇔a=±2
7. a. (x-3)(2y+1)=7
$\left \{ {{x-3=1} \atop {2y+1=7}} \right.$ ⇔$\left \{ {{x=4} \atop {y=3}} \right.$
$\left \{ {{x-3=7} \atop {2y+1=1}} \right.$ ⇔$\left \{ {{x=10} \atop {y=0}} \right.$
$\left \{ {{x-3=-1} \atop {2y+1=-7}} \right.$⇔$\left \{ {{x=2} \atop {y=-4}} \right.$
$\left \{ {{x-3=-7} \atop {2y+1=-1}} \right.$ ⇔$\left \{ {{x=-4} \atop {y=-1}} \right.$
b. (2x+1)(3y-2)=-55
$\left \{ {{2x+1=1} \atop {3y-2=-55}} \right.$ ⇔$\left \{ {{x=0} \atop {y=-53/3}} \right.$
$\left \{ {{2x+1=-1} \atop {3y-2=55}} \right.$ ⇔$\left \{ {{x=-1} \atop {y=19}} \right.$
$\left \{ {{2x+1=5} \atop {3y-2=-11}} \right.$ ⇔$\left \{ {{x=2} \atop {y=-3}} \right.$
$\left \{ {{2x+1=-11} \atop {3y-2=5}} \right.$ ⇔$\left \{ {{x=-5} \atop {y=7/3}} \right.$
8. a. x∈{-8;-7;-6;-5;-4;-3;-2;-1;0;1;2;3;4;5;6;7;8}
S=-8-7-6-5-4-3-2-1+0+1+2+3+4+5+6+7+8=0
b. x∈{ -5;-4;-3;-2;-1;0;1;2;3}
S=-5-4-3-2-1+0+1+2+3=-9
c. x∈{ -19;-18;-17;-16;-15;-14;-13;-12;-11;-10;-9;-9;-7;-6;-5;-4;-3;-2;-1;0;1;2;3;4;5;6;7;8;9;10;11;12;13;14;15;16;17;18;19;20}
S=20
9. a. (x+17)-(24+35)=x+17-59=x-42
b.-32-(y+20)=-32-y-20=-y-52
10. A=b(a-c)-c(a-b)=ab-bc-ac+bc=ab-ac=a(b-c)=-20×(-5)=100
11. a. Bội (-11); ±11;±22;±33
-7: ±14; ±21;±28
5: ±10; ±15; ±20
b. Ước (-10); ±1;±2;±5;±10
15: ±1;±3 ±5±15
22: ±1 ±2 ±22
-24: ±1 ±2 ±3 ±4 ±6 ±8± 12 ±24
