Question

Giải giúp mình nha 1)Tìm x: A)x. ( x^2 - 4 ) = 0 B)( 2x - 3 ) + ( -3x ) - ( x - 5 ) = 40 C)2.( 3 + 6x ) + 8.( x - 5 ) = -52 D)( x^2 - 144 ).( x -5 ).x = 0 E)x^2 - ( 2x + 1 ) - ( 3 - x ) = - ( 5 - x^2 ) 2)Tính hợp lý A)-45.12 + 34.(-45) - 45.54 B)43.( 57 - 33 ) + 33.( 43 - 57 )

Answer 1

Bài 1: 

a) Ta có: \(x\left(x^2-4\right)=0\)

\(\Leftrightarrow x\left(x-2\right)\left(x+2\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x-2=0\\x+2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=2\\x=-2\end{matrix}\right.\)

Vậy: \(x\in\left\{0;2;-2\right\}\)

b) Ta có: \(\left(2x-3\right)+\left(-3x\right)-\left(x-5\right)=40\)

\(\Leftrightarrow2x-3-3x-x+5=40\)

\(\Leftrightarrow-2x+2=40\)

\(\Leftrightarrow-2x=38\)

hay x=-19

Vậy: x=-19

Bài 2: 

a) Ta có: \(-45\cdot12+34\cdot\left(-45\right)-45\cdot54\)

\(=-45\cdot\left(12+34+54\right)\)

\(=-45\cdot100\)

\(=-4500\)

b) Ta có: \(43\cdot\left(57-33\right)+33\cdot\left(43-57\right)\)

\(=43\cdot57-43\cdot33+43\cdot33-33\cdot57\)

\(=43\cdot57-33\cdot57\)

\(=57\cdot\left(43-33\right)\)

\(=57\cdot10=570\)