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C=(1x3+3x5+...+99x101)+(2x4+4x6+...+98x100)
đặt S=1x3+3x5+...+99x101
=>6S=6x(1x3+3x5+...+99x101)
=1x3x(5+1)+3x5x(7-1)+...+97x99x(101-95)+99x101x(103-97)
=1x3x5+1x3x1+3x5x7-1x3x5+....+97x99x101-95x97x99+99x101x103-97x99x101
=1x3x1+99x101x103
=>S=(3+99x101x103):6=171650
=>C=171650+(2x4+4x6+...+98x100)
đặt A=2x4+4x6+...+98x100
=>6A=6x(2x4+4x6+...+98x100)
=>6A=2x4x6+4x6x(8-2)+...+96x98x(100-94)+98x100x(102-96)
=2x4x6+4x6x8-2x4x6+...+96x98x100-94x96x98+98x100x102-96x98x100
=98x100x102
=>A=98x100x102:6=166600
=>C=166600+171650
=>C=338250
B=2x2+4x4+6x6+...+100x100
=2x(4-2)+4x(6-2)+6x(8-2)+...+100x(102-2)
=2x4-4+4x6-8+6x8-12+...+100x102-200
=(2x4+4x6+6x8+...+100x102)-(4+8+12+...+200)
đặt A=2x4+4x6+...+98x100+100x102
=>6A=6x(2x4+4x6+...+98x100+100x102)
=>6A=2x4x6+4x6x(8-2)+...+96x98x(100-94)+98x100x(102-96)+100x102x(104-98)
=2x4x6+4x6x8-2x4x6+...+96x98x100-94x96x98+98x100x102-96x98x100+100x102x104-98x100x102
=100x102x104
=>A=100x102x104:6=176800
=>B=176800-(4+8+12+...+200)
đặt S=4+8+12+..+200
Số số hạng của S là:
(200-4):4+1=50 số
S=(200+4)x50:2=5100
=>B=176800-5100
=>B=171700
Ta có: \(3^x+3^{x+1}+3^{x+2}=351\)
\(\Rightarrow3^x.1+3^x.3+3^x.3^2^{ }=351\)
\(\Rightarrow3^x.1+3^x.3+3^x.9=351\)
\(\Rightarrow3^x.\left(1+3+9\right)=351\)
\(\Rightarrow3^x.13=351\)
\(\Rightarrow3^x=351:13=27\)
\(\Rightarrow x=3\)
3 k mk nha
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───▄▄██▌█ ░Xe chở 100000000 đến đây..
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x-7 = (-3) + (-8)
x-7 = -11
x = -4
Vậy x = -4
|x-3|=43+(-6)
|x-3|=37
=> x-3=37 hoặc x-3=-37
=>x=40 ; x=-34
Vậy x=40 hoặc x=-34
Học tốt nha bạn
a) 27 : x -\(\frac{1}{2}=\frac{15}{7}:5\)
27 : x -\(\frac{1}{2}\)= \(\frac{3}{7}\)
27 : x = \(\frac{3}{7}+\frac{1}{2}\)
27 : x =\(\frac{6}{14}+\frac{7}{14}\)
27 : x = \(\frac{13}{14}\)
x = 27 : \(\frac{13}{14}\)
x = 27 . \(\frac{14}{13}\)
x = \(\frac{378}{13}\)
b) 2 . x - \(\frac{3}{4}\)= \(\frac{15}{9}.\frac{3}{5}\)
2 . x - \(\frac{3}{4}\)= 1
2 . x = 1 + \(\frac{3}{4}\)
2 . x = \(\frac{7}{4}\)
x = \(\frac{7}{4}:2\)
x = \(\frac{7}{8}\)
cho mình đúng nha
