How do you solve the simultaneous equations #4x+5y=0# and #8x-15y=5#?

1 Answer
Apr 11, 2018

Answer:

#x=0.25# and #y=-0.2#

Explanation:

For simultaneous equations you have to know 2 rules:
• Same signs subtract
meaning if both equations have the same sign you subtract to cancel out #x or y#

•Different signs add
meaning if both equations have different signs you add to also cancel out #x or y#

In this case, you will add both equations because they are of different signs

#4x + 5y = 0#
#8x-15y=5#

multiply the first equation by #3# to cancel out #y# values by adding

after multiplying you'll have
#12x+15y=0#
#+#
#8x-15y=5#
now add both equations
#20x=5#
#x=5/20#
#x=0.25#

Substitute the value of #x# in either of the equations

#4x+5y=0#
#4(0.25)+5y=0#
#1+5y=0#
#5y=-1#
#y=-1/5# or #-0.2#

so #x=0.25# and #y=-0.2#