Question

Giải các phương trình sau:

          a) (x + 2)(3 - x) = 0                            b) (25x +15)(5x + 3) = 0

          c) (4x -10)(24 + 5x)  = 0                     d) 2x(x – 3) + 5(x – 3) = 0

Answer 1

a: =>x+2=0 hoặc 3-x=0

=>x=-2 hoặc x=3

b: =>25x+15=0 hoặc 5x+3=0

=>x=-3/5

c: =>4x-10=0 hoặc 5x+24=0

=>x=5/2 hoặc x=-24/5

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

=>x=3 hoặc x=-5/2

Answer 2

`a)`

`(x + 2)(3 - x) = 0`     

`Th1`

`x+2=0`

`=>x=0-2`

`=>x=-2`

`Th2`

`3-x=0`

`=>x=3-0`

`=>x=3`

`b)`

 `(25x +15)(5x + 3) = 0`

`Th1`

`25x +15=0`

`=>25x=-15`

`=>x=-15:25`

`=>x=-15/25`

`=>x=-3/5`

`Th2`

`5x+3=0`

`=>5x=-3`

`=>x=-3/5`

`c)`

`(4x -10)(24 + 5x)  = 0`

`Th1`

`4x -10=0`

`=>4x=10`

`=>x=10/4=5/2`

`Th2`

`24+5x=0`

`=>5x=-24`

`=>x=-24/5`

`d)`

`2x(x – 3) + 5(x – 3) = 0`

`<=>(x – 3).(2x+5)=0`

`Th1`

`x-3=0`

`=>x=0+3`

`=>x=3`

`Th2`

`2x+5=0`

`=>2x=-5`

`=>x=-5/2`

Answer 3

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

`=>`\(\left[{}\begin{matrix}x+2=0\\3-x=0\end{matrix}\right.\)

`=>`\(\left[{}\begin{matrix}x=-2\\x=3\end{matrix}\right.\)

b) \(\left(25x+15\right)\left(5x+3\right)=0\)

`=>`\(\left[{}\begin{matrix}25x+15=0\\5x+3=0\end{matrix}\right.\)

`=>`\(\left[{}\begin{matrix}25x=-15\\5x=-3\end{matrix}\right.\)

`=>x=-3/5`

c) \(\left(4x-10\right)\left(24+5x\right)=0\)

`=>`\(\left[{}\begin{matrix}4x-10=0\\24+5x=0\end{matrix}\right.\)

`=>`\(\left[{}\begin{matrix}4x=10\\5x=-24\end{matrix}\right.\)

`=>`\(\left[{}\begin{matrix}x=\dfrac{5}{2}\\x=-\dfrac{24}{5}\end{matrix}\right.\)

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

\(2x^2-6x+5x-15=0\)

\(2x^2-x-15=0\)

`=>`\(\left[{}\begin{matrix}2x+5=0\\x-3=0\end{matrix}\right.\)

\(\left[{}\begin{matrix}x=-\dfrac{5}{2}\\x=3\end{matrix}\right.\)