Question

Если 2c+3d=17 и 6c+5d=39, то 4(с+d)=?

Answer 1

Ответ:

28

Объяснение:

2с=17-3д 6с=51-9д

51-9д+5д=39 значит 4д=51-39=12 д=3

2с+9=17 значит 2с=8 с=4

4(4+3)=4*7=28

Answer 2

To find the value of 4(c+d), we first need to solve the given system of equations:

1. 2c + 3d = 17
2. 6c + 5d = 39

We can use the method of substitution or elimination to solve this system. Let's use the elimination method:

Step 1: Multiply the first equation by 2 and the second equation by 3 to make the coefficients of c in both equations equal:

1. 2(2c + 3d) = 2 * 17
2. 3(6c + 5d) = 3 * 39

This simplifies to:

1. 4c + 6d = 34
2. 18c + 15d = 117

Step 2: Now, we can eliminate c by subtracting the first equation from the second:

(18c + 15d) - (4c + 6d) = 117 - 34 14c + 9d = 83

Step 3: Solve for d:

9d = 83 - 14c d = (83 - 14c)/9

Step 4: Substitute the value of d back into the first equation to solve for c:

2c + 3[(83 - 14c)/9] = 17 2c + (249 - 42c)/9 = 17 Multiply by 9 to eliminate the fraction: 18c + 249 - 42c = 17 * 9 18c - 42c = 153 - 249 -24c = -96 c = -96 / -24 c = 4

Step 5: Now that we have the value of c, we can find the value of d:

d = (83 - 14 * 4)/9 d = (83 - 56)/9 d = 27/9 d = 3

Step 6: Finally, find 4(c + d):

4(4 + 3) = 4 * 7 = 28

So, 4(c + d) = 28.