Question

1) [7x + 2y = 9,15x + 2y = 11;2) (9x – 2y = -17,[x – 2y = 7;​

Answer 1

Ответ:

Пошаговое объяснение:

7х+2у=9

15х+2у=11. умножим на     (-1)

7х+2у=9

-15х-2у=-11.

Сложим уравнения.

-8х=-2.

х= 1/4.

Из (2) найдем у.

2у=11-15х=11-15*1/4=(44-15)/4=29/4.

у=29/4:2=29/8.=3  5/8.

Ответ: х=1/4 ; у=29/8.

9х-2у=- 17

х-2у=7.

Метод подстановки.

х=7+2у.

9(7+2у)-2у=- 17.

63+18у-2у=-17.

16у=-17-63=-80

у=-80/16=-5.

х=7+2*(-5)=7-10=-3.

Ответ: х=- 3 ; у= -5.

Answer 2

It looks like you have provided two systems of linear equations. Let's work through each of them:

1) Equation 1: 7x + 2y = 9 Equation 2: 15x + 2y = 11

To solve this system, you can use the method of substitution or elimination. Since the second equation is already solved for y, let's use the elimination method to eliminate the y variable.

Subtracting the first equation from the second equation: (15x + 2y) - (7x + 2y) = 11 - 9 8x = 2 x = 2/8 x = 1/4

Now that we have the value of x, we can substitute it back into either of the original equations. Let's use the first equation:

7x + 2y = 9 7(1/4) + 2y = 9 7/4 + 2y = 9 2y = 9 - 7/4 2y = 29/4 y = (29/4) / 2 y = 29/8

So, the solution for the first system of equations is: x = 1/4 y = 29/8

2) Equation 1: 9x - 2y = -17 Equation 2: x - 2y = 7

Again, you can use the elimination method. Subtract the second equation from the first equation:

(9x - 2y) - (x - 2y) = -17 - 7 8x = -24 x = -24/8 x = -3

Now substitute the value of x back into the second equation:

x - 2y = 7 -3 - 2y = 7 -2y = 7 + 3 -2y = 10 y = -10/2 y = -5

So, the solution for the second system of equations is: x = -3 y = -5

To summarize: 1) x = 1/4 y = 29/8

2) x = -3 y = -5