Tinh nhanh
16+18+20=?
tinh tong :B=(-2)+4+(-6)+8+...+(-18)+20
B = (-2) + 4 + (-6) + 8 +...+ (-18) + 20
B = 2 + 2 + 2 + 2
B = 8
tinh nhanh : 18-15+24-13+20-19+75
tinh : (1/19+2/18+3/17+...+18/2+19/1)/1/2+1/3+1/4+...+1/20
Tinh:
1/19 + 2/18 + 3/17 +...+ 18/2 + 19/1
1/2 + 1/3 + 1/4 +...+ 1/19 + 1/20
\(\frac{1}{19}+\frac{2}{18}+\frac{3}{17}+...+\frac{18}{2}+\frac{19}{1}\) = \(\left(\frac{1}{19}+1\right)+\left(\frac{2}{18}+1\right)+...+\left(\frac{18}{2}+1\right)+1\)
= \(\frac{20}{19}+\frac{20}{18}+...+\frac{20}{2}+\frac{20}{20}\)
=\(20.\left(\frac{1}{19}+\frac{1}{18}+...+\frac{1}{2}+\frac{1}{20}\right)\)
=\(20.\left(\frac{1}{20}+\frac{1}{19}+\frac{1}{18}+...+\frac{1}{2}\right)\)
Vì tử số gấp 20 lần mẫu số nên phân số này bằng 20
tinh tong: 2+4-6-8+10+12-14-16+18+20-22-24...-2008
Ta có
2+4-6-8+10+12-14-16+18+20-22-24+...-2008
=(2+4-6-8)+(10+12-14-16)+(18+20-22-24)+...+(2002+2004-2006-2008)
=(-8)+(-8)+(-8)+...+(-8) (251 số hạng (-8) )
=(-8).251
=-2008
tinh nhanh
10-12+14-16+18-20+22-24+26-28+30
10-12+14-16+18-20+22-24+26-28+30=20
mình nhanh nhất đó
Thuc hien phep tinh) A = \(\frac{5.2^{30}.3^{18}-4.3^{20}2^{27}}{5.2^9.2^{19}.3^{19}-7.2^{29}.3^{18}}\)
ʇɐɥʇ ɥuɐɹ uɐq ɔɐɔ ɐl ƃunp ıɥʇ ʎɐp uǝp ɔonp ɔop uɐq ɔɐɔ ɐl ʇǝıq ɥuıɯ ƃunɥu 'ɔonp ɔop ıoɯ ıɐl ɔonƃu ʎɐox ıɐɥd ɐʌ ɔop oɥʞ ɐl ʇɐɹ ıɥʇ ʎɐu ǝɥʇ ʇǝıʌ ɐl ʇǝıq ɥuıɯ
Tinh hop li :
A = \(\frac{5.2^{30}.3^{18}-2^2.3^{20}.2^{27}}{5.2^9.6^{19}-7.2^{29}.3^{18}}\)
\(A=\frac{5.2^{30}.3^{18}-2^2.3^{20}.2^{27}}{5.2^9.6^{19}-7.2^{29}.3^{18}}\)
\(A=\frac{5.2^{30}.3^{18}-2^{29}.3^{20}}{5.2^9.2^{19}.3^{19}-7.2^{29}.3^{18}}\)
\(A=\frac{5.2^{30}.3^{18}-2^{29}.3^{20}}{5.2^{28}.3^{19}-7.2^{29}.3^{18}}\)
\(A=\frac{2^{29}.3^{18}.\left(5.2.1-9\right)}{2^{28}.3^{18}.\left(5.1.3-7.2.1\right)}\)
\(A=\frac{2.1}{1}=2\)
thank you bạn nha, Le Quang Phúc.
tinh tong : A=2+4-6-8+10+12-14-16+18+20-22-24+.......+2004-2006-2008
A=-2008 tick cho tớ nhé nguyen dinh chi kim kết bạn rồi nhé