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16 votes
Solve the system by substitution.
y = -2.x
y = -9x + 21

User Daxu
by
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1 Answer

3 votes

since y=-2x, we can substitute into the second equation to get:

-2x=-9x+21

add 9x

7x=21

divide by 7

x=3

User Claudio Floreani
by
7.1k points