急!!! F.1 Math (20點!!!) 幫幫忙!!!

Jasmine，老土都講一句，唔可以就咁抄答案ｇａ，要明白當中的意思。

而且你要保證將來考試測驗的時候要識自己做，咁先可以。

要尊重學習的過程。　明白嗎？

1.)
　( -a² + 4a - 7) - ( 5a² - 6a + 2)
= -a² + 4a - 7 - 5a² + 6a - 2
= -a² - 5a² + 4a + 6a - 7 - 2
= -6a² + 10a - 9


2.) Expand the following algebraic expressions and express your answers in ascending order of powers of x.

　(1 - 2x)(x + 3)
= (1)(x + 3) - 2x(x + 3)
= x + 3 - 2x² - 6x
= 3 - 5x - 2x²

　(x - 2y)²
= (x - 2y)(x - 2y)
= x(x - 2y) - 2y(x - 2y)
= x² - 2xy - 2xy + 4y²
= 4y² - 4xy + x²

　(x² - 1 + x )(x² - 1 - x)
= x²(x² - 1 - x) - 1(x² - 1 - x) + x(x² - 1 - x)
= x⁴ - x² - x³ - x² + 1 + x + x³ - x -x²
= 1 - 3x² + x⁴