a)a) - Xét tổng :
(5a+8b)+2(−a+2b)(5a+8b)+2(-a+2b)
=5a+8b−2a+4b=5a+8b-2a+4b
=3a+12b⋮3=3a+12b⋮3
→(5a+8b)+2(−a+2b)⋮3→(5a+8b)+2(-a+2b)⋮3
mà 5a+8b⋮35a+8b⋮3
→2(−a+2b)⋮3→2(-a+2b)⋮3
mà (2,3)=1(2,3)=1
→−a+2b⋮3→-a+2b⋮3
b)b) - Xét tổng :
(5a+8b)+(10a+b)(5a+8b)+(10a+b)
=5a+8b+10a+b=5a+8b+10a+b
=15a+9b⋮3=15a+9b⋮3
→(5a+8b)+(10a+b)⋮3→(5a+8b)+(10a+b)⋮3
mà 5a+8b⋮35a+8b⋮3
→10a+b⋮3→10a+b⋮3
c)c) - Xét tổng :
(5a+8b)+(16b+a)(5a+8b)+(16b+a)
=5a+8b+16b+a=5a+8b+16b+a
=6a+24b⋮3=6a+24b⋮3
→(5a+8b)+(16b+a)⋮3→(5a+8b)+(16b+a)⋮3
mà 5a+8b⋮35a+8b⋮3
→16b+a⋮3→16b+a⋮3
6)6)
- Xét x<0x<0
2017x=2016x+x2017x=2016x+x
mà x<0x<0
⇒2016x+x<2016x⇒2016x+x<2016x
⇒2017x<2016x⇒2017x<2016x
- Xét x=0x=0
⇒2016x=2017x=0⇒2016x=2017x=0
hay 2016x=2017x2016x=2017x
- Xét x>0x>0
2017x=2016x+x2017x=2016x+x
mà x>0x>0
⇒2016x+x>2016x⇒2016x+x>2016x
⇒2017x>2016x⇒2017x>2016x
b)b)
- Xét x<0x<0
x2>0x2>0
5x<05x<0
⇒x2>0>5x⇒x2>0>5x
⇒x2>5x⇒x2>5x
- Xét x=0x=0
⇒x2=5x=0⇒x2=5x=0
hay x2=5xx2=5x
- Xét x>0x>0
x2=x.x<5x⇔x<5x2=x.x<5x⇔x<5
x2=x.x=5x⇔x=5x2=x.x=5x⇔x=5
x2=x.x>5x⇔x>5
111111111+4253=?
Gì vậy hả mày !
Tao ko rõ
Mày nghĩ à !
Cái gì đấy !
