Which value of x satisfies both -9x + 4y = 8 and -3x − y = 4 given the same value of y?

Question

A.-1/7
B.-7/9
C.-8/7
D.-9
E.-4/3

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Answer 1 · 2018-07-25T01:51:13

A. #-8/7#

Solve the system of linear equations by elimination.

Equation 1: #-9x+4y=8#

Equation 2: #-3x-y=4#

Multiply Equation 2 by #4#.

#4(-3x-y)=4xx4#

#-12x-4y=16#

Add the two equations.

#-9xcolor(white)(.)+4y=8#
#-12x-4y=16#
#-------#
#-21xcolor(white)(........)=24#

#-21x=24#

Divide both sides by #-21#.

#x=-24/21#

Reduce by dividing the numerator and denominator by #3#.

#x=-8/7#