`#AkaShi`
`a) 12x^2+7x-12`
`=12x^2+16x-9x-12`
`=(12x^2+16x)-(9x+12)`
`=4x(3x+4)-3(3x+4)`
`=(3x+4)(4x-3)`
.............
`b) 5x^2+6xy+y^2`
`=5x^2+xy+5xy+y^2`
`=(5x^2+xy)+(5xy+y^2)`
`=x(5x+y)+y(5x+y)`
`=(5x+y)(x+y)`
....................
`c) 1/4a^4+16b^4`
`=1/4a^4+16b^4+4a^2b^2-4a^2b^2`
`=(1/4a^4+4a^2b^2+16b^2)-4a^2b^2`
`=[(1/2a^2)^2+1/2.2.4.a^2b^2+(4b^2)^2]-4a^2b^2`
`=(1/2a^2+4b^2)^2-(2ab)^2`
`=(1/2a^2+4b^2-2ab)(1/2a^2+4b^2+2ab)`
......................
`x^3-x-30`
`=x^3-3x^2+3x^2+10x-9x-30`
`=(x^3-3x^2)+(3x^2-9x)+(10x-30)`
`=x^2(x-3)+3x(x-3)+10(x-3)`
`=(x-3)(x^2+3x+10)`
