3.12.37+4.20.9+18.43.12 cac ban giai giup minh voi, cam on
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TN
2
MA
21 tháng 10 2014
\(=1994\times867+\left(1994+1\right)\times133\)
\(=1994\times867+1994\times133+133\)
\(=1994\times\left(867+133\right)+133\)
\(=1994\times1000+133=1994000+133=1994133\)
(Cần sử dụng tính chất phân phối giữa phép nhân và phép cộng
\(a\times\left(b+c\right)=a\times b+a\times c\)
Theo cả hai chiều)
MQ
1
20 tháng 2 2021
Bài 35:
b) ĐKXĐ: \(x\notin\left\{5;2\right\}\)
Ta có: \(\dfrac{x+2}{x-5}+3=\dfrac{6}{2-x}\)
\(\Leftrightarrow\dfrac{x+2}{x-5}+3-\dfrac{6}{2-x}=0\)
\(\Leftrightarrow\dfrac{x+2}{x-5}+3+\dfrac{6}{x-2}=0\)
\(\Leftrightarrow\dfrac{\left(x+2\right)\left(x-2\right)}{\left(x-5\right)\left(x-2\right)}+\dfrac{3\left(x-5\right)\left(x-2\right)}{\left(x-5\right)\left(x-2\right)}+\dfrac{6\left(x-5\right)}{\left(x-2\right)\left(x-5\right)}=0\)
Suy ra: \(x^2-4+3\left(x^2-7x+10\right)+6x-30=0\)
\(\Leftrightarrow x^2-4+3x^2-21x+30+6x-30=0\)
\(\Leftrightarrow4x^2-15x-4=0\)
\(\Leftrightarrow4x^2-16x+x-4=0\)
\(\Leftrightarrow4x\left(x-4\right)+\left(x-4\right)=0\)
\(\Leftrightarrow\left(x-4\right)\left(4x+1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-4=0\\4x+1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=4\\4x=-1\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=4\left(nhận\right)\\x=-\dfrac{1}{4}\left(nhận\right)\end{matrix}\right.\)
Vậy: \(S=\left\{4;-\dfrac{1}{4}\right\}\)
Bài 36:
a) Ta có: \(\left(3x^2-5x+1\right)\left(x^2-4\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left(x+2\right)\left(3x^2-5x+1\right)=0\)
mà \(3x^2-5x+1>0\forall x\)
nên (x-2)(x+2)=0
\(\Leftrightarrow\left[{}\begin{matrix}x-2=0\\x+2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-2\end{matrix}\right.\)
Vậy: S={2;-2}
26 tháng 7 2017
1, Ba is a good badminton player .
\(\rightarrow\) He plays badminton well .
2, Lan is a slow runner .
\(\rightarrow\) She runs slowly .
3, Mrs.Thanh is a quick swimmer .
\(\rightarrow\) He swims quickly .
4, Mrs.Vui is a safe cyclist .
\(\rightarrow\) She cycles safely .
5, Lan's father is a careful driver .
\(\rightarrow\) He drives carefully .
6, My mother is a good cook .
\(\rightarrow\) She cooks well .
7, My sister is a beautiful dancer .
\(\rightarrow\) She dances beautifully .
8, Nam and Ba are skillful soccer player .
\(\rightarrow\) They play soccer skillfully .
9, Mr.Tuan and Mr.Nam are careless driver .
\(\rightarrow\) They drives careless .
10, We should finish our homework first .
\(\rightarrow\) We must finish our homework first .
11, Lan must tidy the house everyday .
\(\rightarrow\) Lan has to tidy the house everyday .
12, Ba ought to cook lunch for his mother .
\(\rightarrow\) Ba has to cook lunch for his mother .
26 tháng 7 2017
1. Ba is a good badminton player
= Ba plays badminton well.( ko có goodly nha )
5. Lan's father is a careful taxi driver
= He drives taxi carefuly
6. My mother is a good cook
= She cooks well.
7. My sister is a beautiful dancer.
= She dances beautifully
8. Nam and Ba are skillful soccer players
= They are play soccer skillfully
9. Mr. Tuan and Mr. Nam are careless driver.
= They drive car carlessly
10. We should finish our homework first.
= We must finish our homework first.
11. Lan must tidy the house everyday
= Lan has to tidy the house everyday.
12. She ought to cook lunch for his mother
= Ba has to cook lunch for his mother
S
1 tháng 8 2019
\(\frac{1}{\sqrt{a}+\sqrt{a+1}}=\frac{\sqrt{a+1}-\sqrt{a}}{\left(\sqrt{a}+\sqrt{a+1}\right)\left(\sqrt{a+1}-\sqrt{a}\right)}=\frac{\sqrt{a+1}-\sqrt{a}}{a+1-a}=\sqrt{a+1}-\sqrt{a}\Rightarrow\frac{1}{1+\sqrt{2}}+\frac{1}{\sqrt{2}+\sqrt{3}}+.......+\frac{1}{\sqrt{99}+\sqrt{100}}=-1+\sqrt{2}-\sqrt{2}+\sqrt{3}-......-\sqrt{99}+\sqrt{100}=10-1=9\)
PB
5
HT
12 tháng 4 2020
CÁC PHÂN SỐ ĐÓ LÀ :
1.12/5 x CẢ TỬ VÀ MẪU VỚI 2 THÌ RA SỐ THỨ NHẤT , x VỚI 3 THÌ RA SỐ THỨ HAI VÀ x VỚI 4 THÌ RA PHÂN SỐ THỨ NĂM
3.12.37+4.20.9+18.43.12
= (3.12).37+(4.9).20+18.12.43
=36.37+36.20+18.2.6.43
=36.37+36.20+36.258
=36.(37+20+258)
=36.315
=11340