Разложите на множители
1. 400 - m^2 = (20 - m)(20 + m) 2. 4x^2 - 25 = (2x-5)(2x+5) 3. 2 7/9t^2 -1 = (5/3t - 1)( 5/3t+1) 4. 16a^4 - 81 = (4a^2 -9)(4a^2 +9) 5. (x+1)^2 -16 = (x+1 -4)(x+1+4) = (x-3)(x+5) 6. a^2 -12 a + 36 = (a - 6)^2 7. 16m^2 +24mn +9n^2 = (4m+3n)^2