Please help me with explanation

Step-by-step explanation:

Basically for questions like these, you have to make the denominator a whole number with no surds, so you multiply it by the same numbers but change the sign. Whatever you do at the bottom you have to do at the top so

and then you expand

- 2 + 10x³ - 21x² + 19x - 4

step-by-step explanation:

each term in the second factor is multiplied by each term in the first factor

x²(- 2x² + 4x - 1) - 3x(- 2x² + 4x - 1) + 4(- 2x² + 4x - 1) ← distribute

= - 2 + 4x³ - x² + 6x³ - 12x² + 3x -8x² + 16x - 4

collect like terms

= - 2 + 10x³ - 21x² + 19x - 4 ← in standard form