I need help with three and four

Answer:
Step-by-step explanation:
Part 3 :
We simply expand the brackets
(a+b)² = (a+b)(a+b)
(a+b)(a+b) = a²+ab+ab+b² = a²+2ab+b²
This is part 3 done
Part 4:
We simply expand 3 brackets now:
(2x-1)³ = (2x-1)(2x-1)(2x-1)
We do the first 2 brackets first:
(2x-1)(2x-1) = 4x²-2x-2x+1 = 4x²-4x+1
Now we multiply this by the last bracket:
(4x²-4x+1)(2x-1) = 8x³ -4x²-8x² +4x+2x -1 = 8x³-12x²+6x-1
This is part 4 done
Hope this helped and brainliest please