MATHEMATICS Algebra
Simultaneous Equations
1. 5u + 2v=7
2u - 2v=7

2. 3x - 4y=19
4x - 5y=23

1. u = 2, v = -1.5

2. y = -7, x = -3

Step-by-step explanation:

1) For the following simultaneous equation, we have;

5·u + 2·v = 7(1)

2·u - 2·v = 7(2)

Adding equation (1) to equation (2), gives;

5·u + 2·v + 2·u - 2·v = 14

5·u + 2·u + 2·v- 2·v   = 14

7·u = 14

u = 14/7 = 2u = 2

u = 2

From equation (1), we have;

5·u + 2·v = 7 substituting u = 2 gives;

5×2 + 2·v = 7

2·v = 7  - 5×2 = 7 - 10 = -3

v = -3/2 = -1.5

v = -1.5

2.

3·x - 4·y = 19(1)

4·x - 5·y = 23(2)

Multiplying  equation (1) by 4 and equation (2) by 3 gives;

For equation (1)

4 × (3·x - 4·y) = 4 ×19

12·x - 16·y = 76(3)

For equation (2)

3 × (4·x - 5·y) = 3 × 23

12·x - 15·y = 69(4)

Subtracting equation (3) from equation (4) gives;

12·x - 15·y - (12·x - 16·y) = 69 - 76 = -7

12·x - 15·y - 12·x + 16·y = 69 - 76 = -7

12·x - 12·x - 15·y + 16·y = -7

y = -7

Substituting the value of y = -7 in equation (1), we have;

3·x - 4·y = 19 = 3·x - 4×(-7) = 19

3·x - 4×(-7) = 19

3·x + 28 = 19

3·x = 19- 28  = -9

x = -9/3 = -3

x = -3.

6.9

step-by-step explanation:

simple math really

6 1/2 times 0.6 = 3.9

but if you are just doing 6 and not 6 1/2 then the answer is 3.6