HOC24
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Môn học
Chủ đề / Chương
Bài học
Thay `b=5a+2c` vào `ax^2+bx+c=0`:
`ax^2+(5a+2c)x+c=0`
`=>Delta=(5a+2c)^2-4ac`
`=25a^2+20ac+4c^2-4ac`
`=25a^2+16ac+4c^2`
`=9a^2+(16a^2+16ac+4c^2)`
`=9a^2+(4a+2c)^2>=0`
`=>` ĐPCM
mountains
Choose the best answer:1.___do you go shopping? –Once a week.(How/ Why/How often/ How far)2.__is it from your school to house?-About 1km(How much/How far/ When/Where)3.Yesterday she bought meat,fish___vegetables.(and/ but/ or/ so)4.She is thin,___she is strong.(but/ although/ or/ if)5.Odd one out:(boat/town/ house/crowded)6.Odd one out:(earth/ anything/through/than)7.Odd one out:(there/ them/both/neither)8.Yesterday, she (play/played/plays/ is playing)the piano.9.Hoa:What___you do last night?(was/were/did/ does)Nam: I watched T.V.10.A:Where (is/ are/ was/were)__you last year?B: I was at Cua Lo beach.11.Tìm từ trái nghĩa: quiet ><___(boring/ interesting/ modern/ traditional/noisy)12.Sửa lỗi sai:We are interested of watching cartoons. A B C D13.Not go out at night. A B C D14.This car belongs to my father.It is___ thuộc về (her/him/his/ mine)15.I have a cat. The cat is ____. (my/mine/I/me)16.Odd one out:(arrived/ moved/ laughed/ enjoyed)17.Odd one out:(invited/ decided/ prepared/ wanted) 18.Dung loves sports.He is so (sporty/ sports)19.Ha has a gift. The gift belongs to (Ha/Ha’s)20.When you ride a motorbike.You should wear a( hat/ boot/ helmet/ jacket) to protect
`a/(x+1)+b/(x-2)=(a(x-2)+b(x+1))/((x+1)(x-2))`
`=(ax-2a+bx+b)/(x^2-x-2)`
`=((a+b)x+(-2a+b))/(x^2-x-2)`
``
Theo đề bài: `((a+b)x+(-2a+b))/(x^2-x-2)=(32x-19)/(x^2-x-2)`
Đồng nhất hệ số ta được: `{(a+b=32),(-2a+b=-19):}`
`<=>{(a+b=32),(2a-b=19):}`
`<=>{(3a=51),(a+b=32):}`
`<=>{(a=17),(17+b=32):}`
`<=>{(a=17),(b=15):}`
A.
AB=AE
AD=AC
A vuông
`=>` 2 tam giác bằng nhau
`=>` Đúng
B.
2 tam giác bằng nhau `=> BC=ED`
D. Giống với A
`=>` C sai
1. A.'tropical B.di'saster C.'damage D.'chemical
2. A.pol'lution B. contami'nation C.des'troy D.en'vironment
\(A\left(x\right)=2x^2-x^3\\ B\left(x\right)=x^3-2x^2+3x-1\)
a) `P(x)=A(x)+B(x)`
`=2x^2-x^3+x^3-2x^2+3x-1`
`=(x^3-x^3)+(2x^2-2x^2)+3x-1`
`=3x-1`
b) `P(x)=0`
`3x-1=0`
`3x=1`
`x=1/3`
Số cần tìm có dạng `3overline(ab)`
Tổng các chữ số là 12 `=> 3+a+b=12=>a+b=9`
Số đó nằm giữa 300 và 320 `=>a \in {0;1}`
TH1: `a=0 => b=9=>` Số đó là: 309
309 không chia hết cho 6
TH2: `a=1 => b=8 =>` Số đó là: 318
318 chia hết cho 6
Vậy Keria đang nghĩ đến số 318.
If I were you, I would go there alone.