Внимание на ! 1.observe that 18 = 4² + 1² + 1² + 0². how many of the first fifteen positive integers can be written as the sum of the squares of four integers ? 2. if c is a constant, what is (2 − 3x²)² dx ? 3 if y = xe^x then dy/dx = 4 for each real number x, let [x] be the biggest integer which is less than or equal to x. what can you say about the following three equations ? (i) [p + 3] = [p] + 3 (ii) [p + q] = [p] + [q] (iii) [5p] = 5 [p]