x : 5 = 45
Tính nhanh:
45 x 5 + 45 x 4 + 45
45 x 5 + 45 x 4 + 45
= 45 x 5 + 45 x 4 + 45 x 1
= 45 x (5 + 4 + 1)
= 45 x 10
= 450
= 45 x 5 + 45 x 4 + 1 x 45
=45 x (5 + 4 + 1)
=45 x 10
= 450
x - 5 / 45 + x - 4 / 4 + x - 1 / 49 = x - 49 + x - 45 / 5 + x - 46 / 4
tính nhanh 4/1 x 5+ 4/5 x 9 + 4/9 x 13+⋯+4/41 x 45 + 4/45 x 49
( 45/x-5 )- ( 45/x) = 3/2
\(\dfrac{45}{x-5}-\dfrac{45}{x}=\dfrac{3}{2}\\ \Leftrightarrow\dfrac{1}{x-5}-\dfrac{1}{x}=\dfrac{1}{30}\\ \Leftrightarrow\dfrac{x-\left(x-5\right)}{x\left(x-5\right)}=\dfrac{1}{30}\\ \Leftrightarrow\dfrac{5}{x^2-5x}=\dfrac{1}{30}\\ \Leftrightarrow x^2-5x=600\\ \Leftrightarrow x^2-5x-150=0\\ \Leftrightarrow\left(x+10\right)\left(x-15\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=-10\\x=15\end{matrix}\right.\left(t.m\right)}\)
tìm x biết
(x-5)/45 + (x-4)/46 + (x-1)/49 = x-49 +(x-45)/5 +(x-46)/4
Tìm x bt
x - 5/ 45 + x - 4 / 4 + x - 1 / 49 = x - 49 + x - 45 / 5 + x - 46 / 4
Tìm x
\(\frac{3}{3+5}+\frac{3}{5+7}+\frac{3}{7+9}+...+\frac{3}{43+45}=\frac{x}{45}\)\(\frac{x}{45}\)
cho mình bỏ đi 1 phân số \(\frac{x}{45}\)ở cuối nhé