9
QuizMultiple Choice

Linear Systems of Equations — Test

Question 9 • Mathematics 8

Using the linear combination method, what is the solution to the system of linear equations 7 x minus 2 y is equal to negative 20 and 9 x plus 4 y is equal to negative 6 ?

Answer
A
open paren 2 comma negative 3 close paren
B
open paren negative 2 comma 3 close paren
C
open paren negative 3 comma 2 close paren
D
open paren 3 comma negative 2 close paren

Explanation

Multiply 7x − 2y = −20 by 2 to get 14x − 4y = −40. Add this to 9x + 4y = −6; the y-terms cancel, giving 23x = −46, so x = −2. Substituting into the first equation gives −14 − 2y = −20, so y = 3. The solution is (−2, 3), choice B.

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