1){3х-2у=7 {2х+2у=8 . 2) {7х-0,4у=-15 {4х-0,4у=10.
3){5х-0,6у=-6 {2х-0,3у=16.

1) (x, y) = (3, 1)

{3x-2y=7

{2x+2y=8

{3x-2y=7

{2y=8-2x

3x-(8-2x)=7

x=3

2y=8-2*3

y=1

(x, y) = (3, 1)

{3*3-2*1=7

{2*3+2*1=8

{7=7

{8=8

(x, y) = (3, 1)

2) (x, y) = (-25/3, - 325/3)

{7х-0,4у=-15

{4х-0,4у=10

{7х-0,4у=-15

{-0,4y=10-4x

7x+10-4x=-15

x=-25/3

-0,4y=10-4*(-25/3)

y=-325/3

(x, y) = (-25/3, - 325/3)

{7*(-25/3)-0,4*(-325/3)=-15

{4*(25/3)-0,4*(-325/3)=10

{-15=-15

{10=10

(x, y) = (-25/3, - 325/3)

3) (x, y) = (-38, - 920/30)

{5х-0,6у=-6

{2х-0,3у=16

{5х-0,6у=-6

{x=8+3y/20

5(8+3y/20)-0,6y=-6

y=-920/3

(x, y) = (-38, - 920/30)

{5*(-38)-0,6*(-920/3)=-6

{2*(-38)-0,3*(-920/3)=16

{-6=-6

{16=16

(x, y) = (-38, - 920/30)

если буквы не повторяются

с⁵₂₈=28! /(5! *(28-=28! /(5! *23! )=98280

y=3 cos ( 4x+п/6 ) +3

y`=-12sin(4x+п/6)

  x0=-п/12

y(-п/12)=3 cos ( 4(-п/12)+п/6 ) +3=3cos(-п/3+п/6) +3=3cos(-п/6)+3=

                      =3cos(п/6)+3=3*sqrt{3}/2 +3

y`(-п/12)=-12sin(4*(-п/12)+п/6)=-12sin(-п/6)=-12*(-1/2)=6

у=у(х0)+y`(x0)(x-x0)

y=3*sqrt{3}/2 +3 + 6(x+п/12)=6х +(6+п+3sqrt{3})/2