...z b thay vào là đc

\(\left\{{}\begin{matrix}\left(x^2-2x-9\right)\sqrt{x^2-x-6}=0\left(1\right)\\x+y=0\left(2\right)\end{matrix}\right.\)

ĐK: \(\left[{}\begin{matrix}x\ge3\\x\le-2\end{matrix}\right.\)

Từ (1) <=> \(\left[{}\begin{matrix}x^2-2x-9=0\left(\cdot\right)\\x^2-x-6=0\end{matrix}\right.\) (*) nghiệm không tm đk

<=> \(\left[{}\begin{matrix}x=3\left(I\right)\\x=-2\left(II\right)\end{matrix}\right.\) -> 

Từ (2) => y = -x 

(I) y = -3

(II) y = 2

Với x = 3 và y = -3 => P = 3² + (-3)² + 2020 = 2038

với x = -2 và y = 2 => P = (-2)² + 2² + 2020 = 2028

Theo bài ra, ta có:

\(\dfrac{26+c}{45}=\dfrac{2}{3}\)

-> \(\dfrac{26+c}{45}=\dfrac{30}{45}\)-> 26 + c = 30 -> c = 4

1. He (work) ___are working__________ in the office now.
2. My friend (enjoy)________enjoys_____ hamburgers very much.
3. The students ( look) ____are looking_________ up these new words right now.
4. We always (do) ________do_____ English exercises carefully.
5. The sun (rise) _____rises________ in the east.
6. They (talk) __________are talking___ to John at the moment.
7. The children (sleep) __________sleep___ well for two hours every afternoon.
8. My sister (need) _____needs________ some money for books.
9. It (rain) ______rains_______ very much in the United States.
10. Linda (write) _____is writing________ to David at the moment.
11. Thu (not have) ________doesn't have_____ any apples. She (have) ________have_____ some oranges.
12. Minh (watch) ___watches__________ TV every night. he (watch) ________are watching_____ TV at present.
13. We often (swim) __swim___________ in the river, but today we (go) ______are going_______ fishing.
14. They often (play) _____play________ tennis. They (play) ____________are playing_ tennis at the
moment.
15. Nam (ride) __ride___________ his bike to school everyday, but now he (walk) is walking

Giải: Ta có: NP = 8/7 MP = 8/7 x 28 = 32 cm

Diện tích tam giác MNP là:

S_MNP = NF x MP : 2 = 20 x 28 : 2 = 280 (cm²)

hay ME x NP : 2 = 280 => X x 32 : 2 = 280 => X = 17,5 cm