Question

Find the solution to each system by the addition (elimination) method. Check your answers.

5s + 9t = 6

4s – 3t = 15

 

Answer 1

Elimination method

5s+9t = 6 --------> (1)

4s-3t = 15

Multiple to each side by 3.

4s-9t = 45----> (2)

To eliminate the t value add the equations (1) and (2).

5s+9t = 6

12s-9t = 45

__________

17s = 51

Divide to each side by 17.

17s/17 = 51/17

⇒ s = 3

Substitute the s value in (1).

5*3+9t = 6

15+9t = 6

Subtract 15 to each side.

15-15+9t = 6-15

9t = -9

Divide to each side by 9.

9t/9  = -9/9

⇒ t = -1

Solution s =3, t = -1.

Check:

Substitute the s,t values in given equation (1).

5*3+9*-1 = 6

15-9 = 6

6 = 6

Comments

6 = 6.

The above statement is true.

So, (s, t) = (3, -1) is the soltution of given system.