Tính: a) 5(2x - 1)^2 + 4(x - 1)(x + 3) - 2(5 - 3x)^2; b) (9x - 1)^2 + (1 - 5x)^2 + 2(9x - 1)(1 - 5x)

B1: Tính
a) 5(2x-1)^2+4(x-1)(x+3)-2(5-3x)^2
b) (9x-1)^2+(1-5x)^2+2(9x-1)(1-5x)
c) (a+b+c)^2 + (a+b-c)^2 - 2(a+b)^2
d) (x^2-5x+1)^2+ 2(5x-1)(x^2-5x+1)(5x-1)^2
B2) Chứng minh
a) a(a-b)+10>0
b) (x-3)(x-5)+4>0