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125\(\times\)1008 = 125\(\times\)1000 + 125 \(\times\)8
= 125000 + 1000
= 126000
\(\frac{x}{4}=\frac{18}{x+1}\)
\(\Leftrightarrow x\left(x+1\right)=72\)
\(\Leftrightarrow x=8\)
P/s tham khảo nha
15.(27+18+6)+15(23+12)=15((27+23)+(18+12)+6) =15.(50+30+6)=15.86=1290
(26 + 53 ) +(42 -26-55-53)
=79 + ( 16 -55 - 53 )
=79 + (-39-53)
=79 -39 - 53
=40 - 53 = -13
Gọi tổng trên là A
\(\Leftrightarrow A=1+\left(-2\right)+2^2+...+2^{2014}+\left(-2\right)^{2015}\)
\(\Rightarrow2.A=2.1+\left(-2.2\right)+2.2^2+...+\left(-2.2\right)^{2015}\)
\(\Rightarrow2A=2+\left(-2\right)^2+2^3+...+\left(-2\right)^{2016}\)
\(\Leftrightarrow2A=2+2^2+2^3+...+2^{2016}\)
\(\Rightarrow2A-A=\left(2+2^2+2^3+...+2^{2016}\right)-\left[1+\left(-2\right)+2^3+...+\left(-2\right)^{2015}\right]\)\(\Rightarrow A=2^{2016}-1\)
Kho..................wa.....................troi.....................thi......................lanh.................ret.......................ai........................tich..........................ung.....................ho........................minh.....................cho....................do....................lanh
\(-12+x=5x-20\)
\(-12+20=5x-x=4x\)
\(\Rightarrow8=4x\)
\(\Leftrightarrow x=2\)
45-(5-2x)^2=4375
-(5-2x)^2=45-4375
-(10-4x)=-4330
-10+4x=-4330
4x=-4330+10
4x=-4320
x=-1080
B= 1.99+2.98+2.97+...98.2+99.1
=1.99+2.(99-1)+3.(99-2)+...+98.(99-97)+99.(99-98)
=1.99+2.99-1.2+3.99-2.3+...+98.99-97.98+99.99-98.99
=(1.99+2.99+3.99+...+98.99+99.99)-(1.2+2.3+3.4+...+97.98+98.99)
=99.(1+2+3+...+98+99)-(1.2+2.3+3.4+...+97.98+98.99)
=99.4950-(1.2+2.3+3.4+...+97.98+98.99)
=490050-(1.2+2.3+3.4+...+97.98+98.99)
Đặt C=1.2+2.3+3.4+...+97.98+98.99
=> 3C=1.2.3+2.3.3+3.4.3+...+97.98.3+98.99.3
=1.2.3+2.3.(4-1)+...+98.99.(100-97)
=1.2.3+2.3.4-1.2.3+...+98.99.100-97.98.99
=98.99.100
=> A=(98.99.100):3=323400
Vậy B=490050-323400=166650
=1.99+2.(99-1)+3.(99-2)+4.(99-3)+......+99.(99-98)
=99.(1+2+3+.......+99)-(2+2.3+3.4+........+98.99)
=99.(1+99).99:2-98.99.100:3
=99.50.99-98.33.100
=490050-323400=166650