Question

Tìm x

a) 4(x+2) - 7(2x - 1) + 9(3x - 4)=30

b) 2(5x - 8) - 3(4x - 5) = 4(3x - 4) + 11

c) 5x(1 - 2x) - 3x(x + 18) = 0

d) 5x - 3{4x - 2[4x - 3(5x - 2)]} = 182

E đang cần gấp lắm ạ, cảm ơn ạ:)

Answer 1

a) 4(x+2) - 7(2x - 1) + 9(3x - 4)=30

⇔4x+8 - 14x + 7 + 27x - 36 = 30

⇔ 17x = 51

⇔ x = 3

b) 2(5x - 8) - 3(4x - 5) = 4(3x - 4) + 11

⇔ 10x - 16 - 12x + 15 = 12x - 16 + 11

⇔ -14x = -4

⇔ x= \(\frac{2}{7}\)

c) 5x(1 - 2x) - 3x(x + 18) = 0

⇔ 5x - 10x\(^2\) - 3x\(^2\) -54x =0

⇔ -13x\(^2\) -49 x = 0

⇔ -x ( 13x + 49 ) =0

\(\Leftrightarrow\left[{}\begin{matrix}x=0\\13x+49=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=\frac{-49}{13}\end{matrix}\right.\)

d) 5x - 3{4x - 2[4x - 3(5x - 2)]} = 182

⇔ 5x - 3[ 4x - 2( 4x - 15x + 6 ) ]= 182

⇔5x - 3 ( 4x - 8x + 30x - 12 ) = 182

⇔ 5x - 3 ( 26x - 12 ) = 182

⇔ 5x - 78x + 36 = 182

⇔ - 73x = 146

⇔ x = -2