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kết bn đi

3 tháng 8 2016

\(B=x^{17}-12.x^{16}+12.x^{15}-12.x^{14}+...-12.x^2+12x-1\)

\(=11^{17}-\left(11+1\right)11^{16}+\left(11+1\right)11^{15}-\left(11+1\right)11^{14}+...-\left(11+1\right)11^2+\left(11+1\right)11-1\)

\(=11^{17}-11^{17}-11^{16}+11^{16}+11^{15}-11^{15}-11^{14}+...-11^3-11^2+11^2+11-1\)

\(=11-1=10\)

Vậy B = 10

3 tháng 11 2016

x=11 suy ra 12=x+1 thay vào A ta có:

A=x^17- (x+1)x^16 + (x+1)x^15 - (x+1)x^14 + .....- (x+1)x^2+(x+1)x -1

= x^17 - x^17 -x^16 + x^16 + x^15 - x^15 - x^14 +.....- x^3 -x^2 + x^2 +x -1

= x-1= 11-1=10

Sửa đề: =11

=>\(\dfrac{x-15}{17}-5+\dfrac{x-36}{16}-4+\dfrac{x-76}{12}-2=11-5-4-2=0\)

=>x-100=0

=>x=100

NV
21 tháng 1

\(\dfrac{x-90}{10}+\dfrac{x-76}{12}+\dfrac{x-58}{14}+\dfrac{x-36}{16}+\dfrac{x-15}{17}=15\)

\(\Leftrightarrow\dfrac{x-90}{10}-1+\dfrac{x-76}{12}-2+\dfrac{x-58}{14}-3+\dfrac{x-36}{16}-4+\dfrac{x-15}{17}-5=0\)

\(\Leftrightarrow\dfrac{x-100}{10}+\dfrac{x-100}{12}+\dfrac{x-100}{14}+\dfrac{x-100}{16}+\dfrac{x-100}{17}=0\)

\(\Leftrightarrow\left(x-100\right)\left(\dfrac{1}{10}+\dfrac{1}{12}+\dfrac{1}{14}+\dfrac{1}{16}+\dfrac{1}{17}\right)=0\)

\(\Leftrightarrow x-100=0\) (do \(\dfrac{1}{10}+\dfrac{1}{12}+\dfrac{1}{14}+\dfrac{1}{16}+\dfrac{1}{17}\ne0\))

\(\Leftrightarrow x=100\)

11 tháng 9 2018

\(\left(1+2\right),y^2-13y+12=y^2-12y-y-12=y\left(y-12\right)+\left(y-12\right)=\left(y+1\right)\left(y-12\right)\)

\(3,x^2-x-30=x^2-6x+5x-30=x\left(x-6\right)+5\left(x-6\right)=\left(x+5\right)\left(x-6\right)\)

\(4,y^2+y-42=y^2-6y+7y-42=y\left(y-6\right)+7\left(y-6\right)=\left(y+7\right)\left(y-6\right)\)

\(5,x^2+3x-10=x^2-2x+5x-10=x\left(x-2\right)+5\left(x-2\right)=\left(x+5\right)\left(x-2\right)\)

\(6,x^2-8x+15=x^2-5x-3x+15=x\left(x-5\right)-3\left(x-5\right)=\left(x-3\right)\left(x-5\right)\)

18 tháng 8 2021

\(\frac{X-90}{10}+\frac{X-76}{12}+\frac{X-58}{14}+\frac{X-36}{16}+\frac{X-15}{17}=15\)

\(\frac{X-90}{10}+\frac{X-76}{12}+\frac{X-58}{14}+\frac{X-36}{16}+\frac{X-15}{17}-15=0\)

\(\frac{X-90}{10}-1+\frac{X-76}{12}-2+\frac{X-58}{14}-3+\frac{X-36}{16}-4+\frac{X-15}{17}-5=0\)

\(\frac{X-100}{10}+\frac{X-100}{12}+\frac{X-100}{14}+\frac{X-100}{16}+\frac{X-100}{17}=0\)

\(\left(X-100\right).\left(\frac{1}{10}+\frac{1}{12}+\frac{1}{14}+\frac{1}{16}+\frac{1}{17}\right)=0\)

=> X-100=0

=> X=100

vậy x=100

f: =>\(\dfrac{14}{3\left(x-4\right)}-\dfrac{x+2}{x-4}=\dfrac{-3}{2\left(x-4\right)}-\dfrac{5}{6}\)

=>28-6(x+2)=-9-5(x-4)

=>28-6x-12=-9-5x+20

=>-6x+16=-5x+11

=>-x=-5

=>x=5

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11 tháng 3 2023

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