英语中怎么将肯定句改成否定句啊？要详细点的，最好把各种情况考虑到。

一.肯定句变成否定句
如果句中有be动词is,am,are
或情态动词must,can等,在其后面直接加not,
she
is
your
mother.
she
isn't
your
mother
2.如果没有be动词或情态动词,加don't,does't或did't
she
likes
playing
football.
she
doesn't
like
playing
football.
二.肯定句变成疑问句
变成一般疑问句
如果有be或情态动词动词就把他们提前,
she
is
your
mother.
is
she
your
mother?
2.如果没有就在前面加do的某种形式,第三人称用does,过去时用did
she
likes
playing
football.
does
she
like
playing
football?
变成特殊疑问句,
要具体分析,看是对什么进行提问,简单来说,
1.对人提问用who,
she
is
your
sister.who
is
your
sister?
2.对事物用what,
the
book
is
on
the
desk.
what
it
is
on
the
desk?
3对时间用when,
she
will
come
back
tomorrow.
when
she
will
come
back?
4.对频率用how
often等等
i
play
football
everyday.
how
often
does
you
play
footall?

1.主系表结构的句子
I
am
a
teacher.
-----
I
am
not
a
teacher.
He
is
in
Beijing.-----
He
is
not
in
Beijing.
We
are
classmates.-----
We
are
not
classmates.
It
was
cold
yesterday.-----
It
was
not
cold
yesterday.
这些句子中都有系词，am，is，are，was，were，只要在系词后面+not
，就变成否定句了。
2.主谓宾的句子
He
runs
fast.-----
He
doesn't
run
fast.
主语是三单人称，do也要用三单形式does
They
learn
from
me.------
They
don't
learn
from
me.
We
went
to
school
by
bike
.-----
We
didn't
go
to
school
by
bike.
谓语动词是过去式，do也要变过去式did
这些句子中都有谓语动词，只要在主语后面+do的适当形式+not
就行了。
3.句中有助动词或情态动词的
I
will
get
up
earlier
tomorrow.-----
I
will
not
get
up
earlier
tomorrow.
She
can
dance
well.-----
She
can't
dance
well.
He
has
gone
abroad.------
He
has
not
gone
abroad.
只需要在助动词或情态动词后面直接+not
，就可以变否定句了。
OK？希望能帮到你啊！