(will give medals) Question 4. 4. Solve the following system of equations by linear combination:

3d – e = 7
d + e = 5

(Points : 1)
There is no solution.
There are an infinite number of solutions.
The solution is (3, 2).
The solution is (2, –1).

Question

(will give medals) Question 4. 4. Solve the following system of equations by linear combination:

3d – e = 7
d + e = 5

(Points : 1) 
        There is no solution.
        There are an infinite number of solutions.
        The solution is (3, 2).
        The solution is (2, –1).

anonymous · Answer

linear combination is the same as elimination.

3d - e = 7
d + e = 5 --->(-3)
----------------
3d - e = 7
-3d - 3e = -15 (result of multiplying by -3)
----------------add
-4e = - 8 -- divide both sides by -4
e = 2
now sub 2 in for e in either equation to find d
3d - e = 7
3d - 2 = 7
3d = 7 + 2
3d = 9
d = 3

solution :  d = 3 and e = 2 or (3,2)

any questions ?