quy đồng mẫu số : 1/4=7/28 ; 2/7= 8/28

 Vì 8/18 > 7/28 nên 2/4 > 1/7

   Vậy Hòa được tặng nhiều hoa hơn 

\(c,\overline{735a2b}⋮̸2;⋮5\Rightarrow b=5\\ \Rightarrow\overline{735a25}⋮9\\ \Rightarrow7+3+5+a+2+5⋮9\\ \Rightarrow22+a⋮9\\ \Rightarrow a=5\\ \Rightarrow\overline{735a2b}=735525\\ b,\overline{5a27b}⋮2;⋮5\Rightarrow b=0\\ \Rightarrow\overline{5a270}⋮9\\ \Rightarrow5+a+2+7+0⋮9\\ \Rightarrow14+a⋮9\\ \Rightarrow a=4\\ \Rightarrow\overline{5a27b}=54270\)

c) \(735525\)
d) \(54270\)

A min khi x-3=-1

=>x=2

A max khi x-3=1

=>x=4

\(t,=\dfrac{3^{64}\cdot7^{24}}{7^{23}\cdot9^{66}}=\dfrac{7}{3^2}=\dfrac{7}{9}\\ u,=\dfrac{5^3\cdot3^4\cdot2^5}{5^2\cdot3^3\cdot2^4}=5\cdot3\cdot2=30\\ v,=\dfrac{3^6\cdot2^{15}}{2^6\cdot3^6\cdot2^8}=2\)

\(\dfrac{3^{64}.49^{12}}{7^{23}.9^{33}}\)

\(=\dfrac{3^{64}.\left(7^2\right)^{12}}{7^{23}.\left(3^2\right)^{33}}\)

\(=\dfrac{3^{64}.7^{24}}{7^{23}.3^{66}}\)

\(=\dfrac{7}{9}\)

a: 6/5-2/3=18/15-10/15=8/15

b: 9/7-5/8=72/56-35/56=37/56

c: 7/6-3/4=14/12-9/12=5/12

d: 9/8-8/9=81/72-64/72=17/72

e: 7/5-7/6=7(1/5-1/6)=7/30

f: 3/4-2/5=15/20-8/20=7/20

g: 4/7-5/6=24/42-35/42=-11/41

i: 6/13-5/11=66/143-65/143=1/143

k: 1-4/5=1/5

m: 2-5/9=18/9-5/9=13/9

n: 3-9/5=15/5-9/5=6/5

p: 4-3/4=16/4-3/4=13/4

a) \(\dfrac{6}{5}-\dfrac{2}{3}=\dfrac{18}{15}-\dfrac{10}{15}=\dfrac{8}{15}\)

b) \(\dfrac{9}{7}-\dfrac{5}{8}=\dfrac{72}{56}-\dfrac{35}{56}=\dfrac{37}{56}\)

c) \(\dfrac{7}{6}-\dfrac{3}{4}=\dfrac{28}{24}-\dfrac{18}{24}=\dfrac{10}{24}=\dfrac{5}{12}\)

d) \(\dfrac{9}{8}-\dfrac{8}{9}=\dfrac{81}{72}-\dfrac{64}{72}=\dfrac{17}{72}\)

e) \(\dfrac{7}{5}-\dfrac{7}{6}=\dfrac{42}{30}-\dfrac{35}{30}=\dfrac{7}{30}\)

h) \(\dfrac{4}{7}-\dfrac{5}{6}=\dfrac{24}{42}-\dfrac{35}{42}=-\dfrac{11}{42}\)

i) \(\dfrac{6}{13}-\dfrac{5}{11}=\dfrac{66}{143}-\dfrac{65}{143}=\dfrac{1}{143}\)

k) \(1-\dfrac{4}{5}=\dfrac{5}{5}-\dfrac{4}{5}=\dfrac{1}{5}\)

m) \(2-\dfrac{5}{9}=\dfrac{18}{9}-\dfrac{5}{9}=\dfrac{13}{9}\)

n) \(3-\dfrac{9}{5}=\dfrac{15}{5}-\dfrac{9}{5}=\dfrac{6}{5}\)

p) \(4-\dfrac{3}{4}=\dfrac{16}{4}-\dfrac{3}{4}=\dfrac{13}{4}\)

a, \(P=\left(x^4-8x^3+16x^2\right)+12x^2-48x+35\)

\(=\left(x^2-4x\right)^2+12\left(x^2-4x\right)+36-1\)

\(=\left(x^2-4x+6\right)^2-1\)

\(=\left[\left(x-2\right)^2+2\right]^2-1\)

\(\ge2^2-1=3\)

Cách khác \(P=\left(x-2\right)^2\left[\left(x-2\right)^2+4\right]+3\ge3\)

Đẳng thức xảy ra khi \(x=2.\)

b, \(xy\le\frac{\left(x+y\right)^2}{4}=9\)

Áp dụng bđt Co6si: \(\frac{1}{x^2}+\frac{1}{y^2}\ge2\sqrt{\frac{1}{x^2}.\frac{1}{y^2}}=\frac{2}{xy}\)

\(Q\ge\frac{102}{xy}+xy=xy+\frac{81}{xy}+\frac{21}{xy}\ge2\sqrt{xy.\frac{81}{xy}}+\frac{21}{9}=\frac{61}{3}.\)

Dấu bằng xảy ra khi \(x=y=3.\)

Mk camon bn nhiều nha =))