F2 math (20points)

1.
45(9x/5 - y)(5y/9 + x)
= 5(9x/5 - y)·9(5y/9 + x)
= (9x - 5y)(5y + 9x)
= (9x + 5y)(9x - 5y)
= (9x)² - (5y)²
= 81x² - 25y²


2.
3a(4b - 1) + 2a(1 - 4b)
= 3a(4b - 1) - 2a(4b - 1)
= (3a - 2a)(4b - 1)
= a(4b - 1)


3.
(5x - 2)(y - 3z) - (2 - 5x)(3y - z)
= (5x - 2)(y - 3z) + (5x - 2)(3y - z)
= (5x - 2)[(y - 3z) + (3y - z)]
= (5x - 2)(y - 3z + 3y - z)
= (5x - 2)(4y - 4z)
= 4(5x - 2)(y - z)


4.
(4x + 2x²)/(2 + x)²
= 2x(2 + x)/(2 + x)²
= 2x/(2 + x)


5.
(2a - 2b)/3a ÷ (b - a)/9ab
= 2(a - b)/3a x 9ab/[-(a - b)]
= -6b


6.
a.
C = 2πr
r = C/2π

b.
A = 2πr² + 2πrh
A = 2π(C/2π)² + 2π(C/2π)h
A = (C²/2π) + Ch

c.
A = (C²/2π) + Ch
A = (22²/2)x(7/22) + 22x3
A = 143