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Số tiền Nam mua sách: \(320000\times\dfrac{1}{4}=80000\) (đồng)
Số tiền Nam mua vở: \(90000:\dfrac{2}{3}=135000\) (đồng)
Số tiền Nam mua dụng cụ học tập: \(320000-\left(80000+135000\right)=105000\) (đồng)
tài nguyên rừng nước ta :
Nằm trong vùng thuộc khu hệ rừng mưa nhiệt đới, rừng nước ta nổi tiếng về tài nguyên gỗ, nhất là đặc sản có giá trị. ta có 14,352 triệu ha rừng, chiếm tỷ lệ 43,8% so với diện tích tự nhiên. 9,3 triệu, trong đó có những rừng mới trồng.
-em tưới nước cho cây xanh tốt hơn
-bón phân cho cây
`B=(2015+2016+2017)/(2016+2017+2018)`
`=2015/(2016+2017+2018)+2016/(2016+2017+2018)+2017/(2016+2017+2018)`
Vì `2015/(2016+2017+2018)<2015/2016`
`2016/(2016+2017+2018)<2016/2017`
`2017/(2016+2017+2018)<2017/2018`
`=>B<A`
Bài 5
B= \(\dfrac{2015}{2016+2017+2018}\)+\(\dfrac{2016}{2016+2017+2018}\)+\(\dfrac{2017}{2016+2017+2018}\)
Ta có:\(\dfrac{2015}{2016}\)>\(\dfrac{2015}{2016+2017+2018}\),\(\dfrac{2016}{2017}\)>\(\dfrac{2016}{2016+2017+2018}\),\(\dfrac{2017}{2018}\)>\(\dfrac{2017}{2016+2017+2018}\)
⇒A>B
a) Ta có: 3x-17=x+3
\(\Leftrightarrow3x-x=3+17\)
\(\Leftrightarrow2x=20\)
hay x=10
b) Ta có: \( \left|x-3\right|-12=\left|-5\right|\)
\(\Leftrightarrow\left|x-3\right|=17\)
\(\Leftrightarrow\left[{}\begin{matrix}x-3=17\\x-3=-17\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=20\\x=-14\end{matrix}\right.\)
Vậy: \(x\in\left\{20;-14\right\}\)
c) Ta có: \(25-\left(x-5\right)=-415-\left(15-415\right)\)
\(\Leftrightarrow25-x+5=-415-15+415\)
\(\Leftrightarrow30-x=-15\)
hay x=45
Vậy: x=45
3x - 17 = x + 3
3x = x+3 +17
3x = x+20
3x-x=20
2x = 20
x= 20:2
x = 10
b ) |x-3| -12 = |-5|
|x-3| = 12 + 5
|x-3|=17
\(\left[{}\begin{matrix}x-3=17\\x-3=-17\end{matrix}\right.\) =>\(\left[{}\begin{matrix}x=17-3\\x=-17-3\end{matrix}\right.\)=>\(\left[{}\begin{matrix}x=14\\x=-20\end{matrix}\right.\)
vậy x= 14 hoặc x= -20
c) 25 -(x-5) = -415 -(15-145)
25-(x-5) = 15
x-5 = 25 -15
x-5 = 10
x = 10 - 5
x = 5
Bn lấy ảnh mik vẽ lên cho dễ ạ cảm ơn bn nhiều nhaaa❤️
a: Xét ΔAFD vuông tại F và ΔCEB vuông tại E có
AD=CB
góc FAD=góc ECB
=>ΔAFD=ΔCEB
=>DF=EB
Xét tứ giác DFBE có
DF//BE
DF=BE
=>DFBE là hình bình hành
b: S CAB=S CAD
=>CH*AB=CK*AD
=>CH*AB=CK*BC
=>CH/BC=CK/AB
Xét ΔCHK và ΔBCA có
CH/BC=CK/BA
góc HCK=góc CBA
Do đó: ΔCHK đồng dạng với ΔBCA
refer
1 . Electricity will be brought to remote areas by the government next year
2 . The problem of energy shortage will be solved by using solar energy
3 . A new hydropower plant will be built to meet the increasing demand by the government
4 . In the coming decades , renewable energy will be used everyday /
5 . Will all the world's oil be used up in the next 100 years ?
6 . Solar panels will be placed on the roofs of houses to produce hot water and electricity
7 . Cold , oil , and gas won't be replaced by alternative energy sources anytime soon
8 . Will fossil fuels be completely replaced by renewable energy in the future ?
1 . Electricity will be brought to remote areas by the government next year
2 . The problem of energy shortage will be solved by using solar energy
3 . A new hydropower plant will be built to meet the increasing demand by the government
4 . In the coming decades , renewable energy will be used everyday /
5 . Will all the world's oil be used up in the next 100 years ?
6 . Solar panels will be placed on the roofs of houses to produce hot water and electricity
7 . Cold , oil , and gas won't be replaced by alternative energy sources anytime soon
8 . Will fossil fuels be completely replaced by renewable energy in the future ?
a,\(\dfrac{2}{3}\)-\(\dfrac{5}{7}\).\(\dfrac{14}{25}\)
=\(\dfrac{2}{3}\)-\(\dfrac{2}{5}\)
=\(\dfrac{4}{15}\)
b,\(\dfrac{-2}{5}\).\(\dfrac{5}{8}\)+\(\dfrac{5}{8}\).\(\dfrac{3}{5}\)
=\(\dfrac{5}{8}\).(\(\dfrac{-2}{5}\)+\(\dfrac{3}{5}\))
=\(\dfrac{5}{8}\).\(\dfrac{1}{5}\)
=\(\dfrac{1}{8}\)
Giải:
a) \(\dfrac{2}{3}-\dfrac{5}{7}.\dfrac{14}{25}=\dfrac{2}{3}-\dfrac{2}{5}=\dfrac{4}{15}\)
b) \(\dfrac{-2}{5}.\dfrac{5}{8}+\dfrac{5}{8}.\dfrac{3}{5}\)
\(=\dfrac{5}{8}.\left(\dfrac{-2}{5}+\dfrac{3}{5}\right)\)
\(=\dfrac{5}{8}.\dfrac{1}{5}\)
\(=\dfrac{1}{8}\)
c) \(\left(\dfrac{1}{2}\right)^2-1\dfrac{1}{2}+0,5.\dfrac{12}{5}+5\%\)
\(=\dfrac{1}{4}-\dfrac{3}{2}+\dfrac{1}{2}.\dfrac{12}{5}+\dfrac{1}{20}\)
\(=\dfrac{-5}{4}+\dfrac{6}{5}+\dfrac{1}{20}\)
\(=0\)
Chúc bạn học tốt!