(2a+5)-5(4a+5) = 2a+5-20a-25 = -18a-20
(4x+5y)^2-(4x-5y)^2 = 16x²+40xy+25y²-16x²+40xy-25y² = 80xy
(b+7c)^2-(7c-b)² = b²+14bc+49c²-49c²+14bc-b²= 28bc
(4-y)(4+y)(16+y^2) = (16-y²)*(16+y²) = 256-y^4
(p-3)^2(p+3)^2 = (p²-9)² = p^4-18p+81
(10-c^2)(10+c^2)(100+c^4) = (100-c^4)*(100+c^4) = 10000-c^8