6q-r+2s=8 2q+3r-s=-9 4q+2r+5s=1

Question

Solve by Elimination

Answer 1

Call equations A, B and C. 2A+C: 16q+9s=17. Call this equation D.

3A+B=20q+5s=15 or 4q+s=3. Call this equation E.

D-4E: 5s=5, so s=1. Therefore, 4q=3-s=2, so q=1/2.

From A, r=6q+2s-8=3+2-8=-3.

The solution is q=1/2, r=-3, s=1.

Check by substitution: A: 3+3+2=8; B: 1-9-1=-9; C: 2-6+5=1. All correct.

Answer 2

Given 6q-r+2s=8

2q+3r-s=-9

4q+2r+5s=1

r=-3, s=1, q=1/2

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