2 giờ 15 phút = 2,25 giờ

30 phút = 0,5 giờ

Quãng đường đi từ nhà Nam đến thị xã là :

\(12.2,25=27\) ( km )

Vận tốc lúc sau là :

27 : 0,5 = 54 km/h

bài toán có hai đáp số vì có thể chia thành hai trường hợp:
Trường hợp 1: A nằm giữa O và B, khi đó OA+AB=OB=>8+2=10(cm)
Trường hợp 2:B nằm giữa O và A, khi đó OB+BA=OA=>OB+2=8=>OB=6(cm)
Vậy bài toán có hai đáp số
1. OB=10cm
2. OB=6cm

tick đúng cho mình nha

2x + 7 = 135

=> 2x = 128

=> x = 64

Ta có : \(\left|\dfrac{1}{3}-x\right|\ge0\) \(\forall\) x

\(\Rightarrow\left|\dfrac{1}{3}-x\right|+5\ge5\) \(\forall\) x

Dấu '' ='' xảy ra \(\Leftrightarrow\) \(\left|\dfrac{1}{3}-x\right|=0\)

\(\Leftrightarrow\)x = \(\dfrac{1}{3}\)

Vậy A_min = 5 \(\Leftrightarrow\) x = \(\dfrac{1}{3}\)

TH1 : Nếu a + c+ b \(\ne\) 0

Áp dụng t/c dãy tỉ số bằng nhau ta có :

\(\dfrac{a+b-2017c}{c}=\dfrac{b+c-2017a}{a}=\dfrac{c+a-2017b}{b}=\dfrac{a+b-2017c+b+c-2017a+c+a-2017b}{c+a+b}=\dfrac{-2015a-2015b-2015c}{a+b+c}=\dfrac{-2015.\left(a+b+c\right)}{a+b+c}=-2015\)( vì a + b + c \(\ne\)0 )

\(\Rightarrow\left\{{}\begin{matrix}a+b-2017c=-2015c\\b+c-2017a=-2015a\\c+a-2017b=-2015b\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}a+b=2c\\b+c=2a\\a+c=2b\end{matrix}\right.\)

Mặt khác , P = \(\left(\dfrac{b+a}{b}\right).\left(\dfrac{c+b}{c}\right).\left(\dfrac{a+c}{a}\right)\)

\(\Rightarrow\)\(\dfrac{2c}{b}.\dfrac{2a}{c}.\dfrac{2b}{a}=\dfrac{2.âbc}{abc}=2\)

TH2 : Nếu a + b+ c = 0

\(\Rightarrow\left\{{}\begin{matrix}a+b=-c\\b+c=-a\\a+c=-b\end{matrix}\right.\)

\(\Rightarrow P=\dfrac{-c}{b}.\dfrac{-a}{c}.\dfrac{-b}{a}\)=-1

Vây ...

Mk ko chắc là TH2 đúng ko nữa

1. Albert Einstein ( die) ......died.... in 1955.

2. Tom ( go) ....went ... to the post office twice yesterday.

3. He (live) ....lived.......... in London from 1980 to 1985.

4. They (sell) ......sold......................... their house several days ago.

5. When (you, see) ................did you see.................................... her?

6. .....Did................... he (come) ..............come................... to see you last night? Yes he did

7. I ( not, meet) ........didn't meet.................. her in the street last Sunday.

8. I (be) .................was.. at home last night.

9. I (study) ......studied......... music when I was at school

10. ...........Did.................. they (sell) .........sell.......................... their house last year?

11. They (not, be) ..weren't....... teachers in 2000.

12. Hung (not, do) .......didn't do ....................................... his home work yesterday

\(\dfrac{x-2}{2}=\dfrac{y-4}{3}=\dfrac{z-8}{5}\)

\(\Rightarrow\dfrac{x-2}{2}+2=\dfrac{y-4}{3}+2=\dfrac{z-8}{5}+2\)

\(\Rightarrow\dfrac{x+2}{2}=\dfrac{y+2}{3}=\dfrac{z+2}{5}\)

\(\Rightarrow\left(\dfrac{x+2}{2}\right)^2=\left(\dfrac{y+2}{3}\right)^2=\left(\dfrac{z+2}{5}\right)^2\)

\(\Rightarrow\dfrac{\left(x+2\right)^2}{4}=\dfrac{\left(y+2\right)^2}{9}=\dfrac{\left(z+2\right)^2}{25}\)

Áp dụng t/c dãy tỉ số bằng nhau ta có :

\(\dfrac{\left(x+2\right)^2}{4}=\dfrac{\left(y+2\right)^2}{9}=\dfrac{\left(z+2\right)^2}{25}=\dfrac{3.\left(y+2\right)^2}{27}\dfrac{\left(x+2\right)^2+3\left(y+2\right)^2-\left(z+2\right)^2}{4+27-25}=\dfrac{24}{6}=4\)\(\Rightarrow\left\{{}\begin{matrix}\left(x+2\right)^2=16\\\left(y+2\right)^2=36\\\left(z+2\right)^2=100\end{matrix}\right.\)

Bạn chia trường hợp rồi tìm x,y,z nhé

1) \(\left(5-2x\right)\left(2x+7\right)=4x^2-25\)

\(\Rightarrow\)\(-4x-4x^2+35=4x^2-25\)

\(\Rightarrow\) \(-4x=4x^2-25-35+4x^2\)

\(\Rightarrow\)\(-4x=8x^2-60\)

\(\Rightarrow\)-4x - 8x² = -60

\(\Rightarrow\)- 2x . ( 2 + 4x) = -60

Bạn lập bảng rồi tính nha