Question

(4x²-25)=(2x+5)(x-3)

Answer 1

`(4x^2-25)=(2x+5)(x-3)`

`<=>(2x-5)(2x+5)-(2x+5)(x-3)=0`

`<=>(2x+5)(2x-5-x+3)=0`

`<=>(2x+5)(x-2)=0`

`<=>` $\left[\begin{matrix} x=\dfrac{-5}{2}\\ x=2\end{matrix}\right.$

Vậy `S={-5/2;2}`

Answer 2

=>{(2x)²-5²)=(2x+5)(x-3)

=>(2x-5)(2x+5)=(2x+5)(x-3)

=>(2x-5)(2x+5)-(2x+5)(x-3)=0

=>(2x+5)(2x-5-x+3)=0

=>2x+5=0 hoac x-2=0

<=>x=-5/2 hoac x=2

Answer 3

\(\left(4x^2-25\right)=\left(2x+5\right)\left(x-3\right)\)

\(\Leftrightarrow\left(2x+5\right)\left(2x-5\right)=\left(2x+5\right)\left(x-3\right)\)

\(\Leftrightarrow\left(2x+5\right)\left(2x-5\right)-\left(2x+5\right)\left(x-3\right)=0\)

\(\Leftrightarrow\left(2x+5\right)\left(2x-5-x+3\right)=0\)

\(\Leftrightarrow\left(2x+5\right)\left(x-2\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}2x+5=0\\x-2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{5}{2}\\x=2\end{matrix}\right.\)

Vậy \(S=\left\{-\dfrac{5}{2};2\right\}\)

Answer 4

`(4x^2-25)=(2x+5)(x-3)`

`=>4x^2-25=2x^2-6x+5x-15`

`=>4x^2-25-2x^2+6x-5x+15=0`

`=>2x^2-10+x=0`

`=>2x^2+5x-4x-10=0 `

`=>x(2x+5)-2(2x+5)=0`

`=>(x-2)(2x+5)=0`

`\(\Leftrightarrow\left[{}\begin{matrix}x-2=0\\2x=-5\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-\dfrac{5}{2}\end{matrix}\right.\)