Đáp án:
`a)`
`x^2-10x+24`
`=x^2-6x-4x+24`
`=x(x-6)-4(x-6)`
`=(x-4).(x-6)`
`b)`
`3x^2-7x+2`
`=3x^2-6x-x+2`
`=3x.(x-2)-1.(x-2)`
`=(3x-1).(x-2)`
`c)`
`x^2-2x-15`
`=x^2-2x-15`
`=x^2+3x-5x-15`
`=x(x+3)-5(x-3)`
`=(x-5).(x+3)`
`d)`
`15-4x-4x^2`
`=-4x^2-10x+6x+15`
`=-(4x^2+10x)+(6x+15)`
`=-2x.(2x+5)+3.(2x+5)`
`=(-2x+3).(2x+5)`
`e)`
`x^2-5x+1`
`=x^2-5x+(25/4)-25/4 +1`
`=[x^2-2. 5/2 .x +(5/2)^2 ]-21/4`
`=(x-5/2)^2-(\sqrt{21/4})^2`
`=(x-5/2)^2-((\sqrt{21})/(2))^2`
`=(x-5/2 -\sqrt{21}/2).(x-5/2 +\sqrt{21}/2)`
`=(x-(5+\sqrt{21})/(2)).(x-(5-\sqrt{21})/(2))`
`f)`
`x^2-x+3`
`g)`
`2x^2-5xy+3y^2`
`=2x^2-3xy-2xy+3y^2`
`=(2x^2-3xy)-(2xy-3y^2)`
`=x.(2x-3y)-y.(2x-3y)`
`=(x-y).(2x-3y)`
`h)`
`2x^2+xy-y^2`
`=2x^2-xy+2xy-y^2`
`=x.(2x-y)+y.(2x-y)`
`=(x+y).(2x-y)`
