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TH1: x ≥ 10 thì phương trình trở thành:
x - 10 - 2(x+1) =0
⇔ x -10 - 2x - 2 = 0
⇔ -x - 12 = 0
⇔ x = -12 (không thỏa mãn)
TH2: -1≤ x < 10 thì ptrình trở thành:
10 - x - 2(x +1) =0
⇔ 10 - x - 2x - 2=0
⇔8 - 3x =0
⇔ x = 8/3 (thỏa mãn)
TH3: x < -1 thì ptrình trở thành:
10 - x - 2(-x-1) =0
⇔ 10 - x +2x +2 =0
⇔12 + x =0
⇔ x = -12 (thỏa mãn)
Vậy ......... ( tự kết luận nha)
Bạn là Wannable ak???
1.A.serious B.symtoms C.sugar D.sauce
2.A.cable B.station C.answer D.latest
3.A.wrong B.weight C.wait D.weather
4.A.math B.month C.both D.with
5.A.teenager B.shortage C.message D.passage
6.A.started B.weighed C.measured D.called
7.A.follow B.allow C.blow D.know
8.A.earth B.earn C.heart D.heard
9.A.headache B.each C.watch D.church
10.A.minority B.gramophone C.robbery D.monument
1.A.serious B.symtoms C.sugar D.sauce
2.A.cable B.station C.answer D.latest
3.A.wrong B.weight C.wait D.weather
4.A.math B.month C.both D.with
5.A.teenager B.shortage C.message D.passage
6.A.started B.weighed C.measured D.called
7.A.follow B.allow C.blow D.know
8.A.earth B.earn C.heart D.heard
9.A.headache B.each C.watch D.church
10.A.minority B.gramophone C.robbery D.monument
~~~Learn Well Trần quang huy~~~
1. I am 20 years old.
Are you 20 years old ?
How old are you ?
2. She met him yesterday.
Did she meet him yesterday ?
Who did she meet yesterday?
3. They like playing football.
Do they like playing football?
What do they like ?
4. It is 5km from my house to my school.
Are there 5km from your house to your school?
How far is it from your house to your school ?
5. They don't like dog a lot.
Do they like dog ?
What animal do they don't like much ?
6. She can speak English well.
Can she speak English well ?
what language can she speak well ?
7. You are a student.
Are you a student ?
What are you ?
8. She loves Nam.
Does she love Nam ?
Who does she love ?
9. He often plays football in her free time.
Does he often play football in his free time ?
WHat sport does he play in his free time ?
10. There are 10 people in my family.
Are there 10 people in your family ?
How many people in your family ?
Đây là lời giải:
a. Xét △ACD và △ABE có :
AB =AC( giả thiết )
Góc A = 90 độ ( giả thiết )
AD= AE ( giả thiết )
➙ △ACD=ΔABE (c-g-c)
b. Theo đề bài : AD=AE ( gt)
➙AB+BD=AC+CE
mà AB = AC (gt)
➙ BD = CE
Vì ΔACD=ΔABE ( chứng minh phần a)
➜ Góc ADC = góc AEB ( 2 góc tương ứng)
Ta có : góc ADC= góc ABE (cmt)
góc \(O_1\) = góc \(O_2\) (đối đỉnh)
➜180 độ-góc ADC-góc\(O_1\)=180độ - gócABE - góc
→ góc DBO = góc ECO
Xét ΔBOD và ΔCOE có:
Góc ADC= góc AEB (cmt)
BD=CE (cmt)
Góc DBP=góc ECO
→ ΔBOD=ΔCOE ( g-c-g)
c. Vì ΔBOD = ΔCOE (cmt)
→ BO = CO ( hai cạnh tương ứng )
Xét ΔBAO và ΔCAO có :
AB =AC (gt)
BO= CO (cmt)
AO là cạnh chung
Góc DAO= góc EAO (cmt)
AO là cạnh chung
→ ΔDAO=ΔCAO (c-g-c)
→ Góc AOD = góc AOE ( hai góc tương ứng )
mà Góc AOD + góc AOE = 180 độ
→ Góc AOD = góc AOE = \(\dfrac{180}{2}\)= 90 độ
→AO ⊥ DE
Chúc bạn học tốt !

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