Đáp án:
a, 27.34+27.66
=27. (34+66)
=27.100
=2700
b,đề tự ghi nhé
=(-115)+(-35)+11+-35
=[(-115)+115]-[(-35)+35]
=0-0
=0
c,{[(20-6).5]-10}:2+(20)^2
={[14.5]-10}:2+400
={70-10}:2+400
=60:2+400
=30+400
=430
c,= 1.1 + 2.2 + 3.3 +...+ 100.100
= 1 ( 2-1) + 2. (3-1) + 3. (4-1) +... + 100 (101 -1)-(16-16)
= 1.2 - 1 + 2.3 - 2 + 3.4 - 3 +...+ 100. 101 - 100-0
= (1.2 + 2.3 + 3.4 + ... + 100. 101) - (1 + 2 + 3+... + 100)-0
= 1.2 + 2.3 + 3.4 + ... + 100. 101-0
= 1.2 + 2.3 + 3.4 + ... + 100. 101-0
= 3( 1.2 + 2.3 + 3.4 + ... + 100. 101)-0
= 1.2.3 + 2.3.3 + 3.4.3 +... + 100.101.3-0
= 1.2.3 + 2.3. (4-1) + 3.4.(5-2) +...+ 100.101.(102-99)-0
= 1.2.3 + 2.3.4 - 1.2.3 + 3.4.5 - 2.3.4 +... + 100.101.102 - 99.100.101-0
= 100.101.102-0
= 343400
2,
a,x={-2;-1;0;1;2;3;4}
b,[31-(x+5)]=121:11
[31-(x+5)]=11
(x+5)=31-11
(x+5)=20
x=20-5
x=15
vậy x=15
c,
3.lxl=56-32
3.lxl=24
lxl=24:3
lxl=8
vậy xE{8;-8}
d,
(x+1)^3=27
(x+1)^3=3^3
x+1=3
x=3-1
x=2
vậy x=2
Chúc bạn học tốt!
