Решите системы уравнений способом подстановки   1. u+2v=7 u^2=4v=13   2. y^2-z=3 y^2+3z=7   3.  m^2+5n=-14 m-2n=7   4. 2k-2t^2=7 3k+5t=20    

1. u = 7-2v (7-2v)^2 + 4v - 13 =0 49 - 28v + 4v^2 + 4v - 13 = 0 4v^2 - 24v + 36 = 0 (:4) v^2 - 6v + 9 = 0 (v - 3)^2 = 0 v =3 u = 7 - 2*3 = 7-6=1 Ответ : v=3, u=1 2. z = -3+y^2 y^2 + 3*(y^2-3)-7=0 y^2 +3y^2 - 9-7 = 0 4y^2 - 16 = 0 4*(y^2-4)=0 y = 2               y=-2 z = 4-3=1       z  = 4-3=0   Ответ : y = 2, z=1; y=-2, z=1 3. m = 7+2n (7+2n)^2 +5n + 14 = 0 49 + 28n + 4n^2 + 5n + 14 = 0 4n^2 + 33n + 65 = 0 D = 1089 - 1040 = 49  n1 = -33+7/8 = -26/8 = -3,25 n2= -33-7/8 = -40/8 = -5 m1 = 7 - 2 * 26/8 = 7-6,5 = 0,5 m2 = 7 - 2*5 = 7-10 = -3 Ответ : n=-3,25,m=0,5 ; n=-5, m=-3 4. 2k = 7+2t^2 k = 7+2t^2/2 3*(7+2t^2/2) + 5t - 20 = 0 6t^2 + 10t - 19 = 0 D = 784 t1 = 1,5 t2 = -19/6 k1 = 5,75 k2 = 13 19/36