jawab pleaseee......

18) c. 2&3
• (4x+5y)(4x-5y)
= 16x² -20xy + 20xy - 25y²
= 16x² - 25y²

• (x+2)(3x-2)
= 3x² - 2x + 6x - 4
= 3x² + 4x - 4

19) b. 1&3
• 5xy(3x-4y)
= 15x²y - 20xy²

• (3a-1)(a+3)
= 3a² +9a -1a - 3
= 3a² + 8a -3