27x^3-54x^2+36x-8 tại x=34

Cho em hỏi là tại sao $n_{O{H}^{-}}= 2n_{H2}+ 2nO$vậy ạ

1. His phone wasn’t on. I left him a message.
A. His phone wasn’t on so that I left him a message.
B.I left him a message though his phone wasn’t on.
C.As his phone wasn’t on, I left him a message.
D. His phone wasn’t on since I left him a message.

2. She arrived at the office. She realised she hadn't turned off the oven.
A. It was until she arrived at the office that she realised she hadn’t turned off the oven.
B. Only after she arrived at the office did she realise she had forgotten to turn off the oven.
C. She realised she hadn’t turned off the oven until she arrived at the office.
D. It wasn’t until she arrived at the office did she realise she hadn’t turned off the oven.
3. He tried hard to complete his thesis as scheduled. He didn’t succeed.                                            A. He tried hard to complete his thesis, although he didn’t succeed.
B. However hard he tried, he couldn’t complete his thesis on schedule.
C. He failed the exam even though he tried hard to complete his thesis as scheduled.
D. He didn’t succeed in completing his thesis on schedule because he didn’t try hard enough.
4. Bats are not rodents. Bats bear a surface resemblance to a winged mouse.
A. Bats are not rodents, although they do bear a resemblance to a winged mouse.
B. Bats are not rodents that bear a surface resemblance to a winged mouse.
C. Bats are not rodents, when they hear a surface resemblance to a winged mouse.
D. Bats are not rodents, if they bear a surface resemblance to a winged mouse.
5. Sam is good-natured. He loses his temper easily, though.
A. Though his temper easily loses, Sam is good-natured.
B. Good-natured as he is, Sam loses his temper easily.
C. However good-natured Sam is, he gets angry very often.
D. Sam is good-natured because he loses his tamper easily.

x^2+x+1/4 tại x=99/2

27x^3+54x^2+36x+8 tại x=-1/3

S = 1+3+...+997+999

a) x^4+2x^3+x^2

b) 5x^2-10xy +5y^2-20z^2

c) x^3-x+3x^2y+3xy^2+y^3-y

d) 2xy-x^2-y^2+16

e) x^3-4x^2-12x+27

rút gọn biểu thức a+10 căn a+25/a-25

Read and write Who, What or Whose

1. ________ is on the team ? John is on the team

2. ________ was behind the tree ? The bear was behind the tree

3 . _________ boots are they ? They are my boots

4 . __________ did you do yesterday ? I visited my grandpa

a) (2x+1)^2-4(x+2)^2=0

b) 3x^2-7x+2

c)x^2-2x-15

d)x^2-10x+9