Thôi để t làm nốt cho
c )
Ta có :
\(x+5⋮2x-1\)
\(\Leftrightarrow2\left(x+5\right)⋮2x-1\)
\(\Leftrightarrow2x+10⋮2x-1\)
\(\Leftrightarrow2x-1+11⋮2x-1\)
\(\Leftrightarrow11⋮2x-1\)
\(\Leftrightarrow2x-1\inƯ\left(11\right)\)
\(\Leftrightarrow2x-1\in\left\{1;-1;11;-11\right\}\)
\(\Leftrightarrow2x\in\left\{2;0;12;-10\right\}\)
\(\Leftrightarrow x\in\left\{1;0;6;-5\right\}\)
a ) \(\left(19x+2.5^2\right):14=\left(13-8\right)^2-4^2\)
\(\Rightarrow\left(19x+2.25\right):14=5^2-16\)
\(\Rightarrow\left(19x+50\right):14=25-16\)
\(\Rightarrow\left(19x+50\right):14=9\)
\(\Rightarrow19x+50=9.14\)
\(\Rightarrow19x+50=126\)
\(\Rightarrow19x=126-50\)
\(\Rightarrow19x=76\)
\(\Rightarrow x=76:19\)
\(\Rightarrow x=4\)
Vậy \(x=4\)
b ) Số lượng số dãy số trên là :
( x - 1 ) : 1 + 1 = x ( số )
Tổng dãy số trên là :
( x + 1 ) . x : 2 = 378
=> ( x + 1 ) . x = 378 . 2
=> ( x + 1 ) . x = 756
=> x = 27 hoặc x = -28
Vậy x = 27 hoặc x = -28
c ) Tự làm nhé
a)\(\left(19x+2\cdot5^2\right)\div14=\left(13-8\right)^2-4^2\)
\(\left(19x+2\cdot25\right)\div14=\left(13-8\right)^2-16\)
\(\left(19x+2\cdot25\right)\div14=5^2-16\)
\(\left(19x+2\cdot25\right)\div14=25-16\)
\(\left(19x+2\cdot25\right)\div14=9\)
\(\left(19x+2\cdot25\right)=9\times14\)
\(\left(19x+2\cdot25\right)=126\)
\(\left(19x+50\right)=126\)
\(19x=126-50\)
\(x=76\div19\)
\(\Rightarrow x=4\)
b) \(1+2+3+4+...+x=378\)
\(\left(1+x\right)\cdot x\div2=378\)
\(\left(1+x\right)\cdot x=378\times2\)
\(\left(1+x\right)\cdot x=756\)
\(\left(1+x\right)\cdot x=28\cdot27\)
\(\Rightarrow x=27\)
c) \(x+5⋮2x-1\)
\(\Rightarrow x\in\left\{\varnothing\right\}\)
vì ko số nào chia hết
