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Tìm x, biết:
3(x+2)(x+5) +5(x+5)(x+10) +7(x+10)(x+17) =x(x+2)(x+17) (x∉−2;−5;−10;−17)
2(x−1)(x−3) +5(x−3)(x−8) +12(x−8)(x−20) −1x−20 =−34 (x∉1;3;8;20)
x+110 +2+111 x+112 =x+113 +x+114
x−1030 +x−1443 +x−595 +x−1488 =0
$\textbf{a)}$
$\dfrac{x-1}{2}+\dfrac{x-2}{5}=\dfrac14+\dfrac{x-7}{10}$
$\Leftrightarrow\dfrac{5(x-1)+2(x-2)}{10}=\dfrac14+\dfrac{x-7}{10}$
$\Leftrightarrow\dfrac{7x-9}{10}=\dfrac14+\dfrac{x-7}{10}$
$\Leftrightarrow14x-18=5+2x-14$
$\Leftrightarrow12x=9$
$\Leftrightarrow x=\dfrac34.$
$\textbf{b)}$
$\dfrac{3-2}{2x-3}=\dfrac25+\dfrac1{2x-3}-\dfrac32$
$\Leftrightarrow1-\dfrac2{2x-3}=-\dfrac{11}{10}+\dfrac1{2x-3}$
$\Leftrightarrow\dfrac{21}{10}=\dfrac3{2x-3}$
$\Leftrightarrow21(2x-3)=30$
$\Leftrightarrow42x=93$
$\Leftrightarrow x=\dfrac{31}{14}.$
a) 3. ( x - 2/5 ) = 0
<=> x = 0 : 3 + 2/5
<=> x = 2/5
( Theo cách lớp 6)
Hoặc cách thông thường nek:
3. ( x - 2/5 ) = 0
x - 2/5 = 0 : 3
x - 2/5 = 0
x = 0 + 2/5
x = 2/5
Mấy câu sau làm như vậy nha!
^^ Chúc học tốt!!!!
$\textbf{b)}$
$\text{Điều kiện: }x\ne1,\ 3,\ 8,\ 20.$
$\dfrac2{(x-1)(x-3)}+\dfrac5{(x-3)(x-8)}+\dfrac{12}{(x-8)(x-20)}-\dfrac1{x-20}=-\dfrac34$
$\Leftrightarrow\left(\dfrac1{x-3}-\dfrac1{x-1}\right)+\left(\dfrac1{x-8}-\dfrac1{x-3}\right)+\left(\dfrac1{x-20}-\dfrac1{x-8}\right)-\dfrac1{x-20}=-\dfrac34$
$\Leftrightarrow-\dfrac1{x-1}=-\dfrac34$
$\Leftrightarrow\dfrac1{x-1}=\dfrac34$
$\Leftrightarrow4=3(x-1)$
$\Leftrightarrow3x=7$
$\Leftrightarrow x=\dfrac73.$
$\textbf{a)}$
Điều kiện: $x\ne-2,\,-5,\,-10,\,-17.$
$\dfrac3{(x+2)(x+5)}+\dfrac5{(x+5)(x+10)}+\dfrac7{(x+10)(x+17)}=\dfrac{x}{(x+2)(x+17)}$
$\Leftrightarrow\left(\dfrac1{x+2}-\dfrac1{x+5}\right)+\left(\dfrac1{x+5}-\dfrac1{x+10}\right)+\left(\dfrac1{x+10}-\dfrac1{x+17}\right)=\dfrac{x}{(x+2)(x+17)}$
$\Leftrightarrow\dfrac1{x+2}-\dfrac1{x+17}=\dfrac{x}{(x+2)(x+17)}$
$\Leftrightarrow\dfrac{x+17-x-2}{(x+2)(x+17)}=\dfrac{x}{(x+2)(x+17)}$
$\Leftrightarrow\dfrac{15}{(x+2)(x+17)}=\dfrac{x}{(x+2)(x+17)}$
$\Leftrightarrow x=15.$