Câu 1:
[(4x+28).3+5.5]:5=35
[(4x+28).3+5.5]=35.5
(4x+28).3+25=175
(4x+28).3=175-25
(4x+28).3=150
4x+28=150:3
4x+28=50
4x=50-28
4x=22
x=22:4
x=5,5
a.\([\)(4x+28).3+5.5\(]\):5=35\(\Leftrightarrow\)4(x+7).3+25=175\(\Leftrightarrow\)4(x+7).3=150\(\Leftrightarrow\)4.(x+7)=50\(\Leftrightarrow\)x+7=\(\frac{25}{2}\)\(\Leftrightarrow\)x=\(\frac{11}{2}\)
b.720:\([\)41-(2x-5)\(]\)=40\(\Leftrightarrow\)41-(2x-5)=18\(\Leftrightarrow\)2x-5=23\(\Leftrightarrow\)x=14
c.3x+8x-30=25\(\Leftrightarrow\)11x=55\(\Leftrightarrow\)x=5
a) [( 4x + 28 ) . 3 + 5.5 ] : 5 = 35
\(\Leftrightarrow\)[( 4x + 28 ) . 3 + 25 ] = 35.5 = 175
\(\Rightarrow\left(4x+28\right).3=175-25=150\)
\(\Rightarrow4x+28=150:3=50\)
\(\Rightarrow4x=50-28=22\)
\(\Rightarrow x=\frac{22}{4}=\frac{11}{2}=5,5\)
b) 720 : [ 41 - ( 2 . x - 5 )] = 40
\(\Rightarrow41-\left(2x-5\right)=720:40=18\)
\(\Rightarrow2x-5=41-18=23\)
\(\Rightarrow2x=23+5=28\)
\(\Rightarrow x=28:2=14\)
c) 3 . x + 8 . x - 30 = 25
\(\Rightarrow x\left(3+8\right)-30=25\)
\(\Rightarrow11x=25+30=55\)
\(\Rightarrow x=55:11=5\)
[(4x+28).3+5.5]:5=35
12x+84+25=35
12x=-94
x=-47/6
