問2題數學題~

1.expand (3x-5y)(3y+5x)

(3x - 5y)(3y + 5x)
=(3x)(3y) + (-5y)(3y) + (3x)(5x) + (-5y)(5x)
=9xy - 15y² + 15x² - 25xy
=15x² - 15y² - 16xy

2.expand (2x² +x-3)(3x-2) and give your ans in ascending order of x
=(2x²)(3x) + (x)(3x) + (-3)(3x) + (2x²)(-2) + (x)(-2) + (-3)(-2)
=6x³ + 3x² - 9x - 4x² - 2x + 6
=6x³ - x² - 11x + 6
=6 - 11x - x² +6x³

1.(3x-5y)(3y+5x)
=3x 乘3y-5y乘3y+3x乘5x-5y乘5x
=9xy-15y²+15x²-25xy
=9xy-25xy-15y²+15x²
= -16xy-15y²+15x²

2.(2x² +x-3)(3x-2)
=2x²乘3x+x乘3x-3乘3x-2x²乘2-2x+3乘2
=6x立方+3x²-9x-4x²-2x+6
=6x立方+3x²-4x²-9x+6
=6x立方-x²-9x+6

1. (3x-5y)(3y+5x)
=9xy-15y²+15x²-25xy
=15x²-16xy-15y²

2. (2x² +x-3)(3x-2)
=6x^3+3x²-9x-4x²-2x+6
=6-11x-x²+6x^3

*6x^3 means 6x既三次方