1) (5x-4) (5x+4) = 25x² + 20x-20x - 16
= 25x² -16
2) (a + b -c) (a + b + c)
a² + ab + ac + ab + b² + bc -ac - bc -c²
a² + 2ab +b² - c²
3) (2x+3y-4z)²
Expand
(2x + 3y - 4z) (2x+3y-4z)
Multiply each term in first trinomial by each term in second trinomial. This is similar to number 2.
4. (3-5y)² = Expand (3-5y) (3-5y)
= 9 -15y - 15y + 25y²
= 9-30y + 25y²
25y² -30y + 9
5) (x²-3)³ = (x² - 3) (x²-3) (x²-3)
= x^6 - 6x^4-3x^4 + 9x² + 18 x² - 27
x^6 -9x ^4 + 27x² - 27
You can do the rest :-)
