giúp mình vs!!

a,Xét tam giác AKC và AKB có:
CA=BA (gt)
CK=BK(gt)
AK :cạnh chung
=>Tam giác AKC=AKB(c.c.c)
=>góc AKC =góc AKB ( vì hai góc tương ứng)
lại có :góc AKC+góc AKB =180 °(vì hai góc kề bù )
=>AKB=AKC =90 °=>AK ⊥ BC (đpcm)
b,Ta có EC ⊥ CB
AK ⊥ CB
=>CE//AK(quan hệ từ vuông góc đến song song)

c, \(\widehat{CEA}+\widehat{CBA}\) =90

\(\widehat{ACB}+\widehat{ABC}\)  = 90

=> \(\widehat{CEA}=\widehat{ACB}\)

Xét tam giác vuông CAE và CAB có:

AC chung

\(\widehat{CEA}=\widehat{ACB}\)

=> Tam giác CAE = CAB

=> CE = CB ( hai cạnh tương ứng)

to become a good student

If you really want to assert yourself, you must have strong determination, whether "running change, a remarkable" remains firm. RESOLVED to do to the same.
1d 24h = 1440 = '. In which at least 7 = 420 'you have to sleep; 1.5h = 90 'you eat; 4h = 240 'you go to school; 1.5h = 90 'you use to communicate with family and loved ones to rest.
Left: 24 - 7 to 1.5 - 4 to 1.5 = 10h = 600 'you use to learn. Each school you should break 1h 10'-15 '. Thus, if you learn in 4 hours continuously (max) 1h then you go play.
So there is too much or too little time for you to use 1d?
With 1bai normal math in textbooks, the average time to resolution is 10'-20 '. If you draft first, you try to find at least two ways to address and choose a shorter way to write in their notebooks. In fact, according to her, her unlimited time to find solutions or as it may apply the solutions that in another post. Limit their time solving the shortest it, for example only a 5 '/ 1bai.
For the lesson of, you read the entire article before 1-2lan. Then closed her book, write down what you remember draft. Opened it, check. Find gist bulleted, writing drafts (drawn haphazardly written restrictions on books). 1lan reread what you wrote. 1lan what reread the book. Closed book, look for the bullet reread and development are based on what you remember. Rereading in books 1lan. Binding reread. So you can be in all yet?
...
I do not write all the way to become a gifted 1hoc. I want you to find out more thinking how fit you to become 1hoc gifted.

study well!

145+43+(-145)+57
=[145+(-145)]+(43+57)
=0+100
=100
Vote mình nhé!

100,100*100,100+200,197=10020,01+200,197=10220,207

k mình nhé 

thank you very much.

๖ۣۜH๖ۣۜU๖ۣۜY  ๖ۣۜR๖ۣۜI๖ۣۜO

10220,207

10220,207

a) 25 + a - (b + c) - a

= 25 - (b + c) = 25 - [25 + (-30)]

= 25 - (-5)

= 30

b) a + b - (c + b)

= a + b - c - b

= a - c

= -13 - 25

= -38

a) 25 + a - (b + c) - a

= 25 - (b + c) = 25 - [25 + (-30)]

= 25 - (-5)

= 30

b) a + b - (c + b)

= a + b - c - b

= a - c

= -13 - 25

= -38

quá đơn giản 

cho 5 k giải cho

(mình trong đội tuyển toán đó nhe nên làm theo đi)