Tim a,b,c,d sao cho
a+b+c+d=1
a+c+d=2
a+b+d=3
a+b+c=4
choa các số a,b,c,d thỏa mãn 3a+2b-c-d=1; 2a+2b-c+2d=2; 4a-2d-3c+d=3; 8a+b-6c+d=4. tính a+b+c+d
Ta có:
3a+2b-c-d=1 (1)
2a+2b-c+2d=2 (2)
4a-2b-2c+d=3 (3)
8a+b-6c+d=4 (4)
(1)+(2)+(3)-(4) vế theo vế ta được:
a+b+c+d=1+2+3-4=2
Vâp a+b+c+d=2
1A gủard B wake C look D prevent
2A to B with C on D at
3A bring B pass C send D take
4 A away B above C for D ảround
Đề bài SGK tiếng anh tập 2 trang 69 bạn nhé
cho 4 sn a,b,c,d sao cho 2b=a+c; 2a=b+d ; c^2+d^2<4 .tim a biet b=2
bài 1
tìm các số a,b,c biết rằng
a+b +c+d =1
a+c+d=2
a+b+d=3
a+b+c=4
\(b=a+b+c+d-\left(a+c+d\right)=1-2=-1\\ c=a+b+c+d-\left(a+b+d\right)=1-3=-2\\ d=a+b+c+d-\left(a+b+c\right)=1-4=-3\\ a=a+b+c+d-b-c-d=1+1+2+3=7\)
b = a + b + c + d − ( a + c + d ) = 1 − 2 = − 1
c = a + b + c + d − ( a + b + d ) = 1 − 3 = − 2
d = a + b + c + d − ( a + b + c ) = 1 − 4 = − 3
a = a + b + c + d − b − c − d = 1 + 1 + 2 + 3 = 7
Circle the word that has the underlined part pronounced differently from the others
1A closure B leisure C pleasure D sure
2A contury B cotnbine C collect D concert
3A fnture B return C picture D culture
4A general B garden C go D get
Circle the word that has the underlined part pronounced differently from the others
1A closure B leisure C pleasure D sure
2A contury B cotnbine C collect D concert
3A future B return C picture D culture
4A general B garden C go D get
Chọn từ có trọng âm ở vị trí khác với các từ còn lại :
1A. eighteen B. handbag C. waiting D. practice
2A. transport (n) B. enter (v) C. cancel (v) D. report (v) 3A. passenger B. horrible C. suggestion D. goalkeeper 4A. hesitate B. merchandise C. quantify D. disappear 5A. drinkable B.possessive C. pilotless D. driverless1A. eighteen B. handbag C. waiting D. practice
2A. transport (n) B. enter (v) C. cancel (v) D. report (v)
3A. passenger B. horrible C. suggestion D. goalkeeper
4A. hesitate B. merchandise C. quantify D. disappear
5A. drinkable B.possessive C. pilotless D. driverless
circle the word with a different strss pattern from others
1a national b physical c arrival d natural
2a classical b ponsonous c logical d pollution
3a nature b classic c degree d debris
4a dramatic b tornado c historic d infury
5a examinee b electronic c scientific d preparation
6a industry b bilology c natural d musical
7a geography b economic c scientific d preparation
8a debris b rainstorm c destroy d shelter
9a climatology b bibliography c communication d radiography
circle the word with a different strss pattern from others
1a national b physical c arrival d natural
2a classical b ponsonous c logical d pollution
3a nature b classic c degree d debris
4a dramatic b tornado c historic d infury
5a examinee b electronic c scientific d preparation
6a industry b bilology c natural d musical
7a geography b economic c scientific d preparation
8a debris b rainstorm c destroy d shelter
9a climatology b bibliography c communication d radiography
cho a/b = c/d .Chứng minh
a) 3a-c/3b-d = 2a+3c/2b+3d
b) 3a-b/3a+d = 3c-a/3c+d
c) a^2 - b^2/c^2-d^2 = 2ab + b^2/2cd + d^2
Đặt a/b=c/d=k
=>a=bk; c=dk
a: \(\dfrac{3a-c}{3b-d}=\dfrac{3bk-dk}{3b-d}=k\)
\(\dfrac{2a+3c}{2b+3d}=\dfrac{2bk+3dk}{2b+3d}=k\)
Do đó: \(\dfrac{3a-c}{3b-d}=\dfrac{2a+3c}{2b+3d}\)
c: \(\dfrac{a^2-b^2}{c^2-d^2}=\dfrac{b^2k^2-b^2}{d^2k^2-d^2}=\dfrac{b^2}{d^2}\)
\(\dfrac{2ab+b^2}{2cd+d^2}=\dfrac{2\cdot bk\cdot b+b^2}{2\cdot dk\cdot d+d^2}=\dfrac{b^2}{d^2}\)
Do đó: \(\dfrac{a^2-b^2}{c^2-d^2}=\dfrac{2ab+b^2}{2cd+d^2}\)
Choose the word which has different stress pattern 1A relate B compass C behind D behave 2A quite B sporty C patient D dislike 3 A behind B funny C story. D muisic 4 A slowly B global C backyard D sunny giúp em với ạ
Cho tỉ lệ thức: a/b = c/d. CM:
a, a/b=c/d=a+4c/b+4d
b, a/b=c/d=3a+2c/3b+2d
c, a/c=b/d=a-2b/c-2d
d, a/c=b/d=5a-2b/5x-2d
Giúp mk vs. Năn nit đóa. Mk sẽ tick choa.
Tớ lỡ tay ấn nhầm, làm tiếp nhá.
Áp dụng tính chất dãy tỉ số bằng nhau, ta có:
\(\dfrac{3a}{3b}=\dfrac{2c}{2d}=\dfrac{3a+2c}{3b+2d}\) (ĐPCM).
c) Ta có:
+) \(\dfrac{a}{c}=\dfrac{b}{d}\) mà \(\dfrac{b}{d}=\dfrac{2b}{2d}\)
\(\Rightarrow\dfrac{a}{c}=\dfrac{2b}{2d}\)
Áp dụng TCDTSBN, ta có:
\(\Rightarrow\dfrac{a}{c}=\dfrac{2b}{2d}=\dfrac{a-2b}{c-2d}\) (ĐPCM)
d) Ta có:
+) \(\dfrac{a}{c}=\dfrac{b}{d}\) mà \(\dfrac{a}{c}=\dfrac{5a}{5b};\dfrac{b}{d}=\dfrac{2b}{2d}\)
\(\Rightarrow\dfrac{5a}{5c}=\dfrac{2b}{2d}\)
Áp dụng TCDTSBN, ta có:
\(\Rightarrow\dfrac{5a}{5c}=\dfrac{2b}{2d}=\dfrac{5a-2b}{5c-2d}\) (ĐPCM)
ĐPCM là điều phải chứng minh nhá bạn, còn áp dụng TCDTSBN là áp dụng tính chất dãy tỉ số bằng nhao
Chúc bạn học tốt!
a) Ta có:
+) \(\dfrac{a}{b}=\dfrac{c}{d}\) mà \(\dfrac{c}{d}=\dfrac{4c}{4d}\)
\(\Rightarrow\)\(\dfrac{a}{b}=\dfrac{4c}{4d}\)
Áp dụng tính chất dãy tỉ số bằng nhau, ta có:
\(\dfrac{a}{b}=\dfrac{4c}{4d}=\dfrac{a+4c}{b+4d}\)(ĐPCM)
b) Ta có:
+) \(\dfrac{a}{b}=\dfrac{c}{d}\) mà \(\dfrac{a}{b}=\dfrac{3a}{3b}\); \(\dfrac{c}{d}=\dfrac{2c}{2d}\)
\(\Rightarrow\) \(\dfrac{3a}{3b}=\dfrac{2c}{2d}\)
Áp dụng tính chất dãy tỉ số bằng nhau, ta có: