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Sau khi bán thì chênh lệch giữa cam và quýt là:
145-15+5=135 (kg)
Số phần mà 135 kg tương ứng là:
8-3=5 (phần)
Số kg cam cửa hàng có ban đầu là:
( 135:3x8)+15=375 (kg)
Số kg quýt của hàng có ban đầu là:
375-145=230 (kg)
Đáp số: Cam 375 kg
Quýt 230 kg
ai k mk mk k lại
Sau khi bán thì chênh lệch giữa cam và quýt là :
145 - 15 + 5 = 135 (kg)
Số phần mà 135 kg tương ứng là :
8 - 5 = 3 (phần)
Số kg cam cửa hàng có ban đầu là :
( 135 : 3 x 8 ) + 15 = 375 (kg)
Số Kg quýt cửa hàng có ban đầu là :
375 - 145 = 230 (kg)
Đáp Số :...
Có Vchóp = 1/3 Sđáy.h = 1/3.a2.2a =2/3a3
Có V. SAMN=V.SABD . 1/4=1/8V.SABCD=>.V.ABCDMN=7/8V.SABCD
=> V.ABCDMN = 7/8.2/3a3 = 7/12a3
Chắc để là tìm max
\(A=\sqrt{xy+3yz+2z^2}+\sqrt{yz+3xz+2x^2}+\sqrt{xz+3xy+2y^2}\)
Với x,y > 0 ta luôn có \(\sqrt{ab}\le\frac{a+b}{2}\)
Dấu "=" xảy ra khi a = b
Áp dụng ta được:
\(2\sqrt{\frac{3}{2}}\sqrt{xy+3yz+2z^2}\le\frac{3}{2}+xy+3yz+2z^2\)
Tương tự: \(2\sqrt{\frac{3}{2}}\sqrt{yz+3xz+2x^2}\le\frac{3}{2}+yz+3xz+2x^2\)
\(2\sqrt{\frac{3}{2}}\sqrt{xz+3xy+2y^2}\le\frac{3}{2}+xz+3xy+2y^2\)
Cộng theo vế ta được :
\(2\sqrt{\frac{3}{2}}A\le\frac{9}{2}+4xy+4yz+4xz+2x^2+2y^2+2z^2\)
Ngoài ra với mọi số thực x,y,z ta có :
\(x^2+y^2+z^2\ge xy+yz+xz\)
Dấu "=" xảy ra khi x = y = z
\(\Rightarrow2\sqrt{\frac{3}{2}}A\le\frac{9}{2}+6\left(x^2+y^2+z^2\right)\le\frac{9}{2}+6\times\frac{3}{4}=9\)
\(\Rightarrow A\le\frac{3\sqrt{6}}{2}\).
Dấu "=" xảy ra khi \(x=y=z=\frac{1}{2}\)
V. Read the text and choose the best answer to fill in the blank. There are two words that are not necessary.
paper -glass- old -metal -symbol-plass- cans -furniture -clear- televisions
We can recycle most things - clothes, shoes, phones, computers, (1) __televisions__________, cars, (2) ____plass________, papers, bottles, and batteries. There are a few things that we can’t recycle - but not many!We can recycle most (3) __paper____________ and card to make new paper. We can recycle (4) ___metal_________ from many different things cans, cars and computers. It’s hard to get new metal so it’s good to recycle metal.We can recycle most types of (5) __glass__________ It’s good to sort the glass into different colours - green, brown and clear glass. Factories can only make new clear glass when 99% of the recycle glass is (6) ___clear_________There’s a recycling (7) ____symbol________ on a lot of the things that we can recycle. There’s sometimes a symbol on the things that we can’t recycle.We have to recycle different types of (8) __furniture__________ in different ways. The recycling symbols on plas help people to sort the different types of plas.
VI. Rearrange the words to make meaningful sentences.
1. How/ Julia/ often/ piano/ the/ does/ play? How often does Julia play the piano ?
2. What/ Helen/ his/ sister/ do/ and/ do/ it’s/ hot/ when? What do Helen and his sister do when it's hot ?
3. Family/ our/ going/ is/ for/ stay/ Nha Trang/ to/ beach/ 5 days/ in. Our family is going to stay in Nha Trang beach for 5 days
4. Don’t/ why/ do/ homework/ before/ you/ out/ going/ your? Why don't you do your homework before going out ?
5. They/ playing/ with/ soccer/ are/ in/ park/ now/ the/ their/ friends. They are playing soccer in the park with their friends now
ta có , theo định lí viet nên : \(\hept{\begin{cases}x_1+x_2=-m\\x_1x_2=\frac{m^2-2}{2}\end{cases}\Rightarrow}x_1x_2=\frac{\left(x_1+x_2\right)^2-2}{2}\Leftrightarrow x_1^2+x_2^2=2\)
.ta có
\(A=2x_1x_2+\frac{3}{x_1^2+x_2^2+2x_1x_2+2}=2x_1x_2+\frac{3}{2x_1x_2+4}\)
Mà \(2=x_1^2+x_2^2\ge2\left|x_1x_2\right|\Rightarrow-1\le x_1x_2\le1\)
trên đọna [-1,1] hàm trên đồng biến nên : \(min=-2+\frac{3}{-2+4}=-\frac{1}{2}\)
\(m=2+\frac{3}{2+4}=\frac{5}{2}\)
=\(\frac{5}{2}\)nha