Neu:
3/p=6
va 3/q=15
thi p-q=???
CMR neu lxl\(\ge\)3 lyl \(\ge\)3 lzl\(\ge\)3 thì \(A=\frac{xy+yz+zx}{xyz}\le1\)
\(\frac{x+5}{3}\)= \(\frac{5}{9}\)
\(\frac{x-2}{27}\)= \(\frac{3}{x-2}\)
tinh nhanh neu co the
\(\frac{3^4.2-3^6}{3^4.17+4.3^4}\)
\(\frac{x+5}{3}=\frac{5}{9}\)
=> ( x + 5 ) x 9 = 3 x 5
=> x + 5 = \(\frac{3\cdot5}{9}\)
=> x + 5 = \(\frac{5}{3}\)
=> x = \(\frac{-10}{3}\)
x+5/3=5/9
(x+5)x3/9=5/9
(x+5)x3=5
x+5=5:3
x+5=5/3
x=5/3-5
x=-10/3
x+5/3=5/9
[x+5]x9=5x3
x+5=[5x3]/9
x+5=5/3
x=5/3-5=-10/3
x-2/27=3/x-2
[x-2]^2=27x3
[x-2]^2=9^2
=>x-2=9
x=9+2=11
Tinh nhanh neu co the:
\(2-\dfrac{2}{3+\dfrac{1}{2}}\)
\(\dfrac{1-\dfrac{1}{\dfrac{3}{4}+1}}{3}\)
a)\(2-\dfrac{2}{3+\dfrac{1}{2}}=2-\dfrac{2}{\dfrac{7}{2}}=\dfrac{10}{7}\)
b)\(\dfrac{1-\dfrac{1}{\dfrac{3}{4}+1}}{3}=\dfrac{1-\dfrac{1}{\dfrac{4}{7}}}{3}=-\dfrac{\dfrac{3}{4}}{3}=-\dfrac{1}{4}\)
CMR:
Neu p va q la hai so nguyen to lon hon 3 thi p^2-q^2 chia het cho 24
Tinh (tinh nhanh neu co the)
\(2-\frac{2}{3+\frac{1}{2}}\) va \(\frac{1-\frac{1}{\frac{3}{4}+1}}{3}\)
\(2-\frac{2}{3+\frac{1}{2}}=2-\frac{2}{\frac{6}{2}+\frac{1}{2}}=2-\frac{2}{\frac{7}{2}}=2-2:\frac{7}{2}=2-\frac{4}{7}=\frac{10}{7}\)
\(\frac{1-\frac{1}{\frac{3}{4}+1}}{3}=1-\frac{1}{\frac{7}{\frac{4}{3}}}=1-\frac{1}{7}:\frac{4}{3}=1-\frac{3}{28}=\frac{25}{28}\)
CMR neu \(a^2+b^2chiahetcho3\)thi a chiahetcho 3 va b chiahet cho 3
CMR neu n la so tn le thi:
\(n^3+3n^2-n-3\) chia het cho 8
ta co n^3+3n^2-n-3=n^2(n+3)/(n+3)=(n^2-1)(n+3)=(n-1)(n+1)(n+3)
doi voi (n+1)(n+3) la hai so lien tiep cach nhau 2 don vi thi n la so le se chia het 8
nhung voi n-1 neu n=1 thi ket qua cua ca h se bang 0 nen toi thay de bai nay thieu dieu kien cua n phai la so le khac 1
cho minh hoi
\(\sqrt[3]{4-\sqrt{15}}\)= ?
neu cach lam
Tinh hop li (neu co the)
a)20-[30-(5-1)\(^2\)]
b)\(2^3\).17\(2^3\).14
c)35.12+65.13
d)136.68+16.272
e)(39.42-37.42):42