Cho hai đường thẳng (d):y=-3x+2 ; (d')x-2y=3
a) Tìm tọa độ giao điểm của 2 đường thẳng trên
b) Gọi (d) cắt Ox tại B,tính diện tích tam giác OAB
c) Cho (d''): y=(-2m+1)x+m+1
Tìm m để 3 đường thẳng đã cho đồng quy
Chứng minh rằng đường thẳng y=mx+5 luôn đi qua M(0;5) với mọi giá trị của ,
Thay tọa độ điểm M(0; 5) vào đường thẳng, ta có:
m.0 + 5 = 5
Vậy đường thẳng luôn đi qua điểm M(0; 5) với mọi giá trị của m
IX. Write conditional sentences type 2, using the cues given.
1. What/ happen/ if/ water pollution/ stop?
______________________________________________________________________
2. We/ be/ happy/ if/ air pollution/ the world/ be/ a/ better place?
______________________________________________________________________
3. If/ there/ be/ no more pollution/ the world/ be/ a better place?
______________________________________________________________________
4. If/I/ be/ you/I/ take/ these bottles/ the bottle bank.
______________________________________________________________________
5. If/ people/ not really care/ the environment/ they/ not try/ save it.
______________________________________________________________________
6. The river/ not be/ so polluted/ if/ factories/ not dump/ waste/ it.
______________________________________________________________________
7. We/ be/ less worried/ if/ oil spills/ not have/ such destructive effects.
______________________________________________________________________
IX. Write conditional sentences type 2, using the cues given.
1. What/ happen/ if/ water pollution/ stop?
`->` What would happen if water pollution stopped?
2. We/ be/ happy/ if/ air pollution/ the world/ be/ a/ better place?
`->` Would we be happy if air pollution in the world were a better place?
3. If/ there/ be/ no more pollution/ the world/ be/ a better place?
`->` Would the world would be a better place if there were no more pollution?
4. If/I/ be/ you/I/ take/ these bottles/ the bottle bank.
`->` If I were you, I would take these bottles to the bottle bank.
5. If/ people/ not really care/ the environment/ they/ not try/ save it.
`->`If people didn't really care the environmet, they wounld not try to save it.
6. The river/ not be/ so polluted/ if/ factories/ not dump/ waste/ it.
`->` The river wouldn't be so polluted if factories didn't dump waste into it.
7. We/ be/ less worried/ if/ oil spills/ not have/ such destructive effects.
`->` We would be less worrried if oild spills didn't have such destructive effects.
_
`-` Công thức: If + S + `V_{QKĐ}`, S + would/could + `V_1`
`*` trong đó: `V_{QKĐ}` gồm:
`+` didn't + `V_1`
`+` `V_{2//ed}`
`+` were.
VIII. Complete the sentences with the verbs in brackets. Use conditional sentences type 2.
1. If people________ (not be) so careless, Earth wouldn’t be in danger.
2. The amount of waste ________ (decrease) if people started to buy reusable packages.
3. Many fish wouldn’t die if factories________ (not dump) so many Chemicals into rivers
and oceans.
4. If people stopped using cars completely, there________ (be) much less pollution.
5. If people________ (buy) more recycled paper, there wouldn’t be so much waste.
6. If we________ (not bury) Chemical waste underground, we ________ (not pollute)
fresh water supplies.
7. Pollution________ (not be) such an issue if governments and common people really
________ (care).
8. What ________ (happen) if the whole world________ (be) full of pollution?
9. If people________ (pay) a little more attention to the environment, the Earth________
(be) greener.
10. If people no longer________ (pollute) the atmosphere, the air________ (soon become)
clean again.
VIII. Complete the sentences with the verbs in brackets. Use conditional sentences type 2.
1. weren't
2. would decrease
3. didn't dump
4. would be
5. bought
6. didn't bury - wouldn't pollute
7. wouldn't be - cared
8. would happen - were
9. paid - would be
10. polluted - would soon become
_
`-` Công thức: If + S + `V_{QKĐ}`, S + would/could + `V_1`
`*` trong đó: `V_{QKĐ}` gồm:
`+` didn't + `V_1`
`+` `V_{2//ed}`
`+` were.
`*` Bài 2.
Gọi `x` là chiều dài của mảnh vườn đó
`y` là chiều rộng của mảnh vườn đó
`(m;x,y>0)`
`-` Vì mảnh vườn hình chữ nhật có chu vi `56m` nên:
`(x+y)*2=56` `=>2x+2y=56` `(1)`
`-` Vì nếu tăng chiều dài `4m` và giảm chiều rộng `2m` thì diện tích tăng `8m^2` nên:
`(x+4)(y-2)=xy-8`
`=> xy -2x +4y - 8 =xy-8`
`=> xy -2x+4y-xy = -8+8`
`=> -2x+4y=0` `(2)`
Từ `(1)` và `(2)`, ta có hệ phương trình: \(\left\{{}\begin{matrix}2x+2y=56\\-2x+4y=0\end{matrix}\right.\)
Giải hệ phương trình, ta được: \(\Leftrightarrow\left\{{}\begin{matrix}x=\dfrac{56}{3}\\y=\dfrac{28}{3}\end{matrix}\right.\left(nhận\right)\)
Vậy, chiều dài của mảnh vườn đó là `56/3 m`.
a.
Do \(EM\perp AB\left(gt\right)\Rightarrow\widehat{EMB}=90^0\)
Xét hai tam giác OAB và và MEB có:
\(\left\{{}\begin{matrix}\widehat{EBM}-chung\\\widehat{AOB}=\widehat{EMB}=90^0\end{matrix}\right.\)
\(\Rightarrow\Delta OAB\sim\Delta MEB\left(g.g\right)\)
b.
Xét hai tam giác AMN và AOB có:
\(\left\{{}\begin{matrix}\widehat{MAN}-chung\\\widehat{AMN}=\widehat{AOB}=90^0\end{matrix}\right.\)
\(\Rightarrow\Delta AMN\sim\Delta AOB\left(g.g\right)\)
\(\Rightarrow\dfrac{AM}{AO}=\dfrac{AN}{AB}\Rightarrow AN.AO=AM.AB\)
c.
Từ \(AN.AO=AM.AB\Rightarrow\dfrac{AO}{AB}=\dfrac{AM}{AN}\)
Xét hai tam giác AMO và ANB có:
\(\left\{{}\begin{matrix}\dfrac{AO}{AB}=\dfrac{AM}{AN}\\\widehat{MAO}-chung\end{matrix}\right.\)
\(\Rightarrow\Delta AMO\sim\Delta ANB\left(c.g.c\right)\)
\(\Rightarrow\widehat{AOM}=\widehat{NBA}\) (1)
Trong tam giác ABE, có \(AO\perp BE\) ; \(EM\perp AB\), mà AO và EM cắt nhau tại N
\(\Rightarrow N\) là trực tâm tam giác ABE \(\Rightarrow BN\) là đường cao thứ 3
\(\Rightarrow BN\perp AE\) tại F hay \(\widehat{NFA}=90^0\)
Xét hai tam giác NFA và NOB có:
\(\left\{{}\begin{matrix}\widehat{NFA}=\widehat{NOB}=90^0\\\widehat{FNA}=\widehat{ONB}\left(\text{đối đỉnh}\right)\end{matrix}\right.\)
\(\Rightarrow\Delta NFA\sim\Delta NOB\left(g.g\right)\Rightarrow\dfrac{NF}{NO}=\dfrac{NA}{NB}\Rightarrow\dfrac{NF}{NA}=\dfrac{NO}{NB}\)
Xét hai tam giác NFO và NAB có:
\(\left\{{}\begin{matrix}\dfrac{NF}{NA}=\dfrac{NO}{NB}\left(cmt\right)\\\widehat{ONF}=\widehat{BNA}\left(\text{đối đỉnh}\right)\end{matrix}\right.\)
\(\Rightarrow\Delta NFO\sim\Delta NAB\left(c.g.c\right)\)
\(\Rightarrow\widehat{NOF}=\widehat{NBA}\) (2)
(1);(2) \(\Rightarrow\widehat{NOF}=\widehat{AOM}\) \(\Rightarrow OA\) là phân giác \(\widehat{FOM}\)
VII. Complete the sentences with the verbs in brackets. Use conditional sentences type 1.
1. If the air in a City________ (get) very polluted, it can make people’s eyes burn.
2. If we dump all sorts of Chemicals into rivers, we________ (not be) able to swim in them
in the future.
3. Many wildlife habitats will be destroyed if people________ (keep) polluting the
environment.
4. If we all use public transport more, we________ (help) reduce air pollution.
5. If we________ (not stop) over-fishing the oceans, many species________ (become)
extinct.
6. If everyone________ (recycle) paper, metal and glass, we ________ (not produce) so
much rubbish.
7. We________ (have) dirty seafood if we________ (dump) rubbish into the sea.
8. If global warming________ (continue), temperatures________ (rise) even higher.
9. If light pollution________ (keep) growing, you________ (not be) able to see even the Big
Dipper at night.
10. We________ (threaten) our own existence if we________ (not cut down) the waste
rapidly.
VII. Complete the sentences with the verbs in brackets. Use conditional sentences type 1.
1. gets
2. will not be
3. keep
4. will help
5. don't stop, will become
6. recycle - will not produce
7. will have - dump
8. continues - will rise
9. keeps - will not be
10. will threaten - don't cut down
_
`-` Công thức: If + S + `V_{HTĐ}`, S + will/can + `V_1`
`*` trong đó: `V_{HTĐ}` gồm:
`+` don't/doesn't + `V_1`
`+` `V_{1//s//es}`
`+` am/is/are.
VI. Choose the best answer to complete the sentences.
1. The river water is severely polluted, mostly________ the dumping of raw sewage.
A. due to B. lead to C. because D. so
2. Sudden changes in water temperature can ________ mass killings of fish, plants, or
amphibians.
A. come up B. result in C. dump into D. thank to
3. Water pollution________ the death of all forms of life in the water bodies.
A. occurs B. results of C. creates D. leads to
4. ________ plastic takes so long to break down, it pollutes the land and ocean.
A. Because B. Due to C. Even if D. Although
5. Many flights were cancelled ________ the smoke from forest fires.
A. so B. because C. because of D. result in
6. ________the garbage dump smells terrible, no one lives around there.
A. Because of B. As C. As a result of D. Even though
7. ________the grain consumption is rising, forests will be cut to provide more room for
planting crops.
A. since B. Although C. unless D. Due to
8. Grace didn’t love nature, ________ she wasn’t happy when her group went camping in a
jungle.
A. but B. and C. because D. so
9. Thousands of fish were killed ________ a discharge of poisonous Chemicals from a
nearby factory.
A. because B. lead to C. result in D. as a result of
10. ________the fog, there were no take-oils from the airport yesterday.
A. Since B. Because C. Owing to D. Thanks to
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