How do you solve the system of equations #3x - 4y = 10# and #x + 4y = - 21#?

1 Answer
seol
Jul 28, 2017

#y=73/16=4.5625#
#x=-157/4=-39.25#

Explanation:

#3x-4y=10#
#x+4y=-21#

use second equation to create a equation for #x# --
#x=-4y-21#

now plug that into the first equation:

  • #3(-4y-21)-4y=10#
  • #-12y-63-4y=10# multiply by distributive property
  • #-16y-63=10# add like terms
  • #-16y=10+63#
  • #-16y=73#
  • #y=73/16=4.5625#

plugging back into the #x# equation --

#x=-4(73/16)-21=-157/4#
#x =-39.25#

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