omoxnn dit qu un entier k est olympique s il existe 4 entiers a b c et d tous premiers avec k tel que k divise a^4 +b^4 +c^4 +d^4 .Soit n un entier naturel quelconque
montrer que n^2 −1 divise a^4 +b^4 +c^4 +d^4
Given the position vectors v_1 = 2i−2j and v_2 =2j
a) show that the unit vector in the direction of v_1 −v_2 = (1/(√5))(i−2j)
b) Write down the equation of the line that contains
the position vectors v_1 and v_2
c) Find the cosine of the angle between v_1 and v_2