ai chỉ em 6 bài này với tìm x. a)(x-289)x47 = 0 b)54(84-x) = 54x c)7 x x -10 =704 d)928 - (31+ x )x = 128 B3 a)2x + 3x=1505 b)5x - x =4088

Đáp án:

Giải thích các bước giải: $\begin{array}{l}a)\left( {x - 289} \right) \times 47{\rm{ }} = {\rm{ }}0\\ \Leftrightarrow x - 289 = 0\\ \Leftrightarrow x = 289\\b)54\left( {84 - x} \right){\rm{ }} = {\rm{ }}54x\\ \Leftrightarrow x - 84 = x\\ \Leftrightarrow 0x = 84\\ \Rightarrow Khong\,co\,gia\,tri\,nao\,cua\,x\,thoa\,man\\c)7{\rm{ }} \times {\rm{ }}x{\rm{ }} - 10{\rm{ }} = 704\\ \Leftrightarrow 7 \times x = 704 + 10\\ \Rightarrow 7 \times x = 714\\ \Leftrightarrow \,\,\,\,\,\,\,\,x = 714:7\\ \Leftrightarrow \,\,\,\,\,\,\,\,x = 102\\B3:\\a)2x{\rm{ }} + {\rm{ }}3x = 1505\\\,\, \Leftrightarrow \,\,\,\,\,\,\,5x\,\,\,\,\,\, = 1505\\\, \Leftrightarrow \,\,\,\,\,\,\,x\,\,\,\,\,\,\,\,\, = 1505:5\\\, \Leftrightarrow \,\,\,\,\,\,\,x\,\,\,\,\,\,\,\,\, = 301\\b)5x{\rm{ }} - {\rm{ }}x{\rm{ }} = 4088\\ \Leftrightarrow \,\,\,\,\,\,4x\,\,\,\,\,\,\, = 4088\\ \Leftrightarrow \,\,\,\,\,\,x\,\,\,\,\,\,\, = 4088:4\\ \Leftrightarrow \,\,\,\,\,\,x\,\,\,\,\,\,\, = 1022\end{array}$

a) (x-289)*47=0

⇒ x-289=0÷47=0

⇒ x=0+289=289

b) 54(84-x)=54

⇒ 84-x=54÷54=1

⇒ x=84-1=83

c) 7*x-10=704

⇒ 7x=704+10=714

⇒ x=714/7=102

d) 928-(31+x)=128

⇒ 31+x=928-128=800

⇒ x=800-31=769

B3:

a) 2x+3x=1505

⇒ 5x=1505

⇒ x=1505/5=301

b) 5x-x=4088

⇒ 4x=4088

⇒ x=4088/4=1022