Tính giá trị biểu thức
a, A=(3/4 : 2/3) : 3/5
b, B= 3/4 : ( 2/5 : 3/5)
c, C = ( 11/12 : 33/16 ) × 3/5
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a: \(A=\dfrac{16^5\cdot15^5}{2^{10}\cdot3^5\cdot5^4}=\dfrac{2^{20}\cdot3^5\cdot5^5}{2^{10}\cdot3^5\cdot5^4}=2^{10}\cdot5=5120\)
b: \(B=\dfrac{2^{15}\cdot3+2^{19}\cdot10}{2^{12}\cdot26}=\dfrac{2^{15}\left(3+2^4\cdot10\right)}{2^{13}\cdot13}=2^2\cdot\dfrac{163}{13}=\dfrac{652}{13}\)
a) (2/5 x 25/29) + (3/5 x 25/29)
= (50/145) + (75/145)
= 125/145
b) (5/2 x 3/7) - (3/14 : 6/7)
= 15/14 - (3/14 x 7/6)
= 15/14 - 1/2
= (30/28) - (14/28)
= 16/28
= 4/7
c) (15/4 : 5/12) - (6/5 : 11/15)
= (15/4 x 12/5) - (6/5 x 15/11)
= 180/20 - 90/55
= 9 - 18/11
= (99/11) - (18/11)
= 81/11
= 7 4/11
a) (2/3) + (20/21 x 3/2 x 7/5)
= 2/3 + (60/210)
= 2/3 + 2/7
= (14/21) + (6/21)
= 20/21
b) (5/17 x 21/32 x 47/24 x 0)
= 0
c) (11/3 x 26/7) - (26/7 x 8/3)
= (286/21) - (208/21)
= 78/21
= 3 9/21
= 3 3/7
a) (25/8) : x = 5/16
=> (25/8) x (16/5) = x
=> 4 = x
b) x + (7/15) = 6/15
=> x = (6/15) - (7/15)
=> x = -1/15
c) x : (28/49) = 7/12
=> x x (49/28) = 7/12
=> x = (7/12) x (28/49)
=> x = 1/2
a) 6 x x = (5/8) : (3/4)
=> 6x = (5/8) x (4/3)
=> 6x = 20/24
=> 6x = 5/6
=> x = (5/6) / 6
=> x = 5/36
câu,b,không,đủ,thông,tin,nhan,bạn.
bÀI LÀM
a) x4+x3+2x2+x+1=(x4+x3+x2)+(x2+x+1)=x2(x2+x+1)+(x2+x+1)=(x2+x+1)(x2+1)
b)a3+b3+c3-3abc=a3+3ab(a+b)+b3+c3 -(3ab(a+b)+3abc)=(a+b)3+c3-3ab(a+b+c)
=(a+b+c)((a+b)2-(a+b)c+c2)-3ab(a+b+c)=(a+b+c)(a2+2ab+b2-ac-ab+c2-3ab)=(a+b+c)(a2+b2+c2-ab-ac-bc)
c)Đặt x-y=a;y-z=b;z-x=c
a+b+c=x-y-z+z-x=o
đưa về như bài b
d)nhóm 2 hạng tử đầu lại và 2hangj tử sau lại để 2 hạng tử sau ở trong ngoặc sau đó áp dụng hằng đẳng thức dề tính sau đó dặt nhân tử chung
e)x2(y-z)+y2(z-x)+z2(x-y)=x2(y-z)-y2((y-z)+(x-y))+z2(x-y)
=x2(y-z)-y2(y-z)-y2(x-y)+z2(x-y)=(y-z)(x2-y2)-(x-y)(y2-z2)=(y-z)(x2-2y2+xy+xz+yz)
\(=\dfrac{3}{5}+\dfrac{8}{15}:\dfrac{2}{7}=\dfrac{3}{5}+\dfrac{28}{15}=\dfrac{9}{15}+\dfrac{28}{15}=\dfrac{37}{15}\)
\(=\dfrac{7}{8}+\dfrac{7}{3}-\dfrac{11}{12}=\dfrac{77}{24}-\dfrac{11}{12}=\dfrac{55}{24}\)
Câu a :
\(\dfrac{5}{12}+\dfrac{3}{4}+\dfrac{1}{3}\\ =\dfrac{5}{12}+\dfrac{9}{12}+\dfrac{4}{12}=\dfrac{3}{2}\)
câu b :
\(\dfrac{1}{4}+\dfrac{3}{7}+\dfrac{11}{14}\\ =\dfrac{7}{28}+\dfrac{12}{28}+\dfrac{22}{28}=\dfrac{41}{28}\)
câu c :
\(\dfrac{1}{4}+\dfrac{3}{12}+\dfrac{12}{36}\\ =\dfrac{3}{12}+\dfrac{3}{12}+\dfrac{4}{12}\\ =\dfrac{10}{12}=\dfrac{5}{6}\)
a) \(A=\left(\dfrac{3}{4}:\dfrac{2}{3}\right):\dfrac{3}{5}=\left(\dfrac{3}{4}\cdot\dfrac{3}{2}\right)\cdot\dfrac{5}{3}=\dfrac{9}{8}\cdot\dfrac{5}{3}=\dfrac{15}{8}\)
b) \(B=\dfrac{3}{4}:\left(\dfrac{2}{5}:\dfrac{3}{5}\right)=\dfrac{3}{4}:\left(\dfrac{2}{5}\cdot\dfrac{5}{3}\right)=\dfrac{3}{4}:\dfrac{2}{3}=\dfrac{3}{4}\cdot\dfrac{3}{2}=\dfrac{9}{8}\)
c) \(C=\left(\dfrac{11}{12}:\dfrac{33}{16}\right)\cdot\dfrac{3}{5}=\left(\dfrac{11}{12}\cdot\dfrac{16}{33}\right)\cdot\dfrac{3}{5}=\dfrac{4}{9}\cdot\dfrac{3}{5}=\dfrac{4}{15}\)
a.
A=\(\left(\dfrac{3}{4}:\dfrac{2}{3}\right):\dfrac{3}{5}\)
=\(\left(\dfrac{3}{4}.\dfrac{3}{2}\right):\dfrac{3}{5}\)
=\(\dfrac{9}{8}:\dfrac{3}{5}\)
=\(\dfrac{9}{8}.\dfrac{5}{3}=\dfrac{45}{24}=\dfrac{15}{8}\)
b.
B=\(\dfrac{3}{4}:\left(\dfrac{2}{5}:\dfrac{3}{5}\right)\)
=\(\dfrac{3}{4}:\left(\dfrac{2}{5}.\dfrac{5}{3}\right)\)
=\(\dfrac{3}{4}:\dfrac{2}{3}=\dfrac{3}{4}.\dfrac{3}{2}\)
=\(\dfrac{9}{8}\)
c.
C=\(\left(\dfrac{11}{12}:\dfrac{33}{16}\right).\dfrac{3}{5}\)
=\(\left(\dfrac{11}{12}.\dfrac{16}{33}\right).\dfrac{3}{5}\)
=\(\dfrac{4}{9}.\dfrac{3}{5}=\dfrac{12}{45}\)
=\(\dfrac{4}{15}\)