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schepotkina [342]
4 years ago
12

Solve using substitution. (C&D) 2C+3D=1 -3C+D=15

Mathematics
2 answers:
frozen [14]4 years ago
8 0
Equation 2
-3c+d=15
d=15+3c

Substitute into eq 1
2c+3(15+3c)=1
2c+45+9c=1
11c=-44
c=-44/11

c=-4

Sub into eq 1

2(-4)+3d=1
-8+3d=1
3d=9
d=9/3

d=3

Verify:
2(-4)+3(3)=1
-8+9=1
1=1 -- True.
tatiyna4 years ago
8 0
  2c + 3d =  1 ⇒ 2c + 3d = 1      ⇒ 2c + 3d = 1
-3c +  d = 15 ⇒ 3(-3c + d) = 15 ⇒ -<u>9c + 3d = 15</u>
                                                               -7c = 16
                                                               -<u>7c</u> = <u>16</u>
                                                               -7      - 7
                                                                 c = -2 2/7
                                                       2(2 2/7) + 3d = 1
                                                           4 4/7 + 3d = 1
                                                          <u>-4 4/7           -4 4/7</u>
                                                                       3d = -3 4/7
                                                                       <u>3d</u> = <u>-3 4/7</u>
                                                                        3          3
                                                                         d = -1 4/21
                                                                   (c, d) = (-2 2/7, -1 4/21)
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