Tính
2^3 +3x(-1phan 2)^0x(1 phan 2)^2x4+ơ(-2)^2:1phan2]:8
ý b 3^2x1 phan 243x 81^x1phan33
dien dau <,>,=
1phan2+ 1phan4... 1
1phan 5+ 2 phan 13...1
1phan 12+ 2 phan 14 ...1
1phan 2 +2phan 3... 1
1phan2+ 1phan4 < 1
1phan 5+ 2 phan 13 < 1
1phan 12+ 2 phan 14 < 1
1phan 2 +2phan 3 > 1
(1phan 2x4+1 phan 4x6+1 phan 6x8+1phan 8x10)xy 1phan 3
1- 1 phan 2 - 1 phan 2 ^2 - 1phan 2^3 - 1phan 2^4-....- 1phan 2^10 .> 1phan 2^11
chung minh rang : 1 phan 2 mu 2 + 1 phan 2 mu 3 + 1 phan 2 mu 4 + .......+ 1phan 2 mu 11 < 1
Ta thấy:
1/22<1/1*2; 1/3^2<1/2*3;...;1/2^11<1/10*11
=> tổng đó nhỏ hơn 1/1*2+1/2*3+...+1/10*11
= 1-1/2+1/2-1/3+...+1/10-1/11
=1-1/11<1
=> tổng đó nhỏ hơn 1
Thuc hien phep tinh :
a) 4 phan 5 + -7 phan 15 . 1, 25
b) 2 phan 5 + 3 phan 5 . ( 4 1phan2 - 3,25)
\(\frac{4}{5}+\frac{-7}{15}.1,25\)
\(=\frac{4}{5}+\frac{-7}{12}\)
\(=\frac{13}{60}\)
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a) \(\frac{4}{5}\)+\(\frac{-7}{15}\) x \(1,25\)
= \(\frac{4}{5}\)+ \(\frac{-7}{15}\)x \(\frac{5}{4}\)
= \(\frac{4}{5}\)+\(\frac{-7}{12}\)
= \(\frac{48}{60}\)+ \(\frac{-35}{60}\)
= \(\frac{13}{60}\)
b \(\frac{2}{5}\)+ \(\frac{3}{5}\)x \(\left(4\frac{1}{2}-3,25\right)\)
= \(\frac{2}{5}\)+\(\frac{3}{5}\)x \(\left(\frac{9}{2}-\frac{13}{4}\right)\)
=\(\frac{2}{5}\)+\(\frac{3}{5}\)x\(\frac{5}{4}\)
=\(\frac{2}{5}\)+\(\frac{3}{4}\)
= \(\frac{8}{20}\)+\(\frac{15}{20}\)
=\(\frac{23}{20}\)
Tinh
1phan 2 +1 phan 3 + 1 phan 6
\(\frac{1}{2}+\frac{1}{3}+\frac{1}{6}=\frac{3+2+1}{6}=\frac{6}{6}=1\)
\(\frac{1}{2}+\frac{1}{3}+\frac{1}{6}=\frac{3}{6}+\frac{2}{6}+\frac{1}{6}=\frac{6}{6}=1\)
\(\frac{1}{2}\)+\(\frac{1}{3}\)+\(\frac{1}{6}\)=\(\frac{3}{6}\)+\(\frac{2}{6}\)+\(\frac{1}{6}\)=\(\frac{5}{6}\)+\(\frac{1}{6}\)=\(\frac{6}{6}\)=1
1phan 2 cong 1 phan 3 cong 1 phan 5 bang bao nhieu
\(\frac{1}{2}+\frac{1}{3}+\frac{1}{5}=\frac{31}{30}\)
1phan 2 cong 1phan 6 cong 1 phan 12 cong 1phan 20 cong 1phan 30 cong mot phan 42 cong mot phan 56 cong mot phan 72 =????
1) - Phan tich cac da thuc sau thanh nhan tu :
a) 14x2y2 - 21xy2 + 28x2y d) 2 phan 7 x(3y -1 )-2 phan 7y (3y-1)
b) x3 -3x2 + 3x- 1 e) (x+y)2-4x2
c) 27x2+1phan 8 f) (x+y)3-(x-y)3
2) tim x biet
a) x2(x+1)+2x(x+1)=0 b) x(3x-2)-5(2-3x)=0
c) 4 phan 9 -25x2=0 d) x2-x+phan4=0
3) tinh nhanh cac gia tri bieu thuc sau :
a) 17.91,5+170.0,85 b) 20162-162
c) x(x-10-y(1-x)tai x=2001va y = 2999
2.a là x=0 , x=-1, x=-2
2.b là x=2/3 , x=-5