\(a)(2x+5)*18=14*9=>(2x+5)*18=126=>2x+5=126:18=7=>2x=7-5=2=>x=2:2=1\)nhé =)
\(a,\dfrac{2x+5}{9}=\dfrac{14}{18}\\ \Rightarrow\dfrac{2x+5}{9}=\dfrac{7}{9}\\ \Rightarrow2x+5=7\\ \Rightarrow2x=2\\ \Rightarrow x=1\)
\(b,\dfrac{x}{15}=\dfrac{3}{y}\\ \Rightarrow xy=45\)
\(\Rightarrow\left(x,y\right)\in\left\{\left(-9;-5\right);\left(-15;-3\right)\right\}\)
b, \(xy=15\Rightarrow x;y\inƯ\left(15\right)=\left\{-1;-3;-5;-15\right\}\)
| x | -1 | -3 | -5 | -15 |
| y | -15(loại) | -5(loại) | -3 | -1 |
b,x15=3y⇒xy=45b,x15=3y⇒xy=45
⇒(x,y)∈{(−9;−5);(−15;−3)}
