x + 12 = 12 + x = 13
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1/4 x 12/13 + 1/6 x 12/13 + 1/8 x 12/13
= 12/13 x (1/4 + 1/6 + 1/8 )
= 12/13 x 13/14
= 1/2
9/13 x 7/12 + 9/13 x 5/12 - 9/13
= 9/13 x (7/12 + 5/12 - 1)
= 9/13 x 0
= 0
4/13 x 5/12 + 4/13 x 7/12 - 4/3
= 4/13 x (5/12 + 7/12) - 4/3
= 4/13 x 1 - 4/3
= 4/13 - 4/3
= -40/39
\(\Rightarrow\frac{x+2}{10^{10}}+\frac{x+2}{11^{11}}-\frac{x+2}{12^{12}}-\frac{x+2}{13^{13}}=0\)
\(\Rightarrow\left(x+2\right)\left(\frac{1}{10^{10}}+\frac{1}{11^{11}}-\frac{1}{12^{12}}-\frac{1}{13^{13}}\right)=0\)
Vì \(\frac{1}{10^{10}}+\frac{1}{11^{11}}-\frac{1}{12^{12}}-\frac{1}{13^{13}}\ne0\)
=>x+2=0
=>x=-2
Vậy x=-2
a) 35 x 12 + 65 x 13
= 35 x 12 + 65 x (12+1)
=35 x 12 + 65 x 21 + 65
=12 x (65 + 35) + 65
= 12 x 100 + 65
= 1200 + 65
= 1265
b) (37 x 13 -13) : (24 + 37 x 12)
= [ 37 x (12+1) - 13 ] : (24 + 37 x 12)
=( 37 x 12 + 37 - 13) : ( 24 +37 x 12)
=( 37 x 12 +24) : (24 + 37 x 12)
=\(1\)
Ta có nhận xét phần b hai tích chia cho nhau mà 2 tích giống nhau vậy kết quả là \(1\)
35 x 12 + 65 x 13 = 1265
( 37 x 13 - 13) : (24 + 37 x 12) = 1
=>
\(\frac{x+2}{10^{10}}+\frac{x+2}{11^{11}}-\frac{x+2}{12^{12}}-\frac{x+2}{13^{13}}=0\)
=>\(\left(x+2\right).\left(\frac{1}{10^{10}}+\frac{1}{11^{11}}-\frac{1}{12^{12}}-\frac{1}{13^{13}}=0\right)\)
vì \(\frac{1}{10^{10}}>\frac{1}{11^{11}}>\frac{1}{12^{12}}>\frac{1}{13^{13}}=>\frac{1}{10^{10}}+\frac{1}{11^{11}}-\frac{1}{12^{12}}-\frac{1}{13^{13}}\ne0\)
=>x+2=0
=>x=-2
tick nhé
\(\frac{x+2}{10^{10}}+\frac{x+2}{11^{11}}=\frac{x+2}{12^{12}}+\frac{x+2}{13^{13}}\)
\(=>\frac{x+2}{10^{10}}+\frac{x+2}{11^{11}}-\frac{x+2}{12^{12}}-\frac{x+2}{13^{13}}=0\)
\(=>\left(x+2\right).\left(\frac{1}{10^{10}}+\frac{1}{11^{11}}-\frac{1}{12^{12}}-\frac{1}{13^{13}}\right)=0\)
Vì \(\frac{1}{10^{10}}>\frac{1}{11^{11}}>\frac{1}{12^{12}}>\frac{1}{13^{13}}\)
Nên \(\frac{1}{10^{10}}+\frac{1}{11^{11}}-\frac{1}{12^{12}}-\frac{1}{13^{13}}\)khác 0
Suy ra: x+2=0
x =0 - 2
x = -2
TICK NHA
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
\(\dfrac{12}{1\cdot5}+\dfrac{12}{5\cdot9}+...+\dfrac{12}{97\cdot101}\)
\(=3\left(\dfrac{4}{1\cdot5}+\dfrac{4}{5\cdot9}+...+\dfrac{4}{97\cdot101}\right)\)
\(=3\left(1-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{9}+...+\dfrac{1}{97}-\dfrac{1}{101}\right)\)
=3*100/101
=300/101
\(x+12=13\)
\(x=13-12\)
\(x=1\)
k mk nha
x = 1 nha bn