Question

Solve the system of linear equations using substitution. Use a pencil and paper. Which expression would be easier to substitute into the other​ equation, in order to solve this​ problem? Explain your reasoning.

x=4y-9
x+4y=3

Answer 1

(- 3, 1.5)

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Given system:

• x = 4y - 9
• x + 4y = 3

The first expression is ready to be substituted as no further operation is required to simplify it.

• 4y - 9 + 4y = 3
• 8y - 9 = 3
• 8y = 12
• y = 12/8
• y = 1.5

Find x:

• x = 4*1.5 - 9
• x = 6 - 9
• x = - 3