How do you solve the system of equations #2p + 3q = 10# and #2q - 4p = 44#?

1 Answer
Aug 13, 2017

See a solution process below:

Explanation:

Step 1) Solve each equation for #4p#:

Equation 1:

#2p + 3q = 10#

#2p + 3q - color(red)(3q) = 10 - color(red)(3q)#

#2p + 0 = 10 - 3q#

#2p = 10 - 3q#

#color(red)(2) * 2p = color(red)(2)(10 - 3q)#

#4p = (color(red)(2) * 10) - (color(red)(2) * 3q)#

#4p = 20 - 6q#

Equation 2:

#2q - 4p = 44#

#-color(blue)(44) + 2q - 4p + color(red)(4p) = -color(blue)(44) + 44 + color(red)(4p)#

#-44 + 2q - 0 = 0 + 4p#

#-44 + 2q = 4p#

#4p = -44 + 2q#

Step 2) Because the left side of each equation is #4p# we can equate the right side of each equation and solve for #q#:

#20 - 6q = -44 + 2q#

#color(red)(44) + 20 - 6q + color(red)(6q) = color(red)(44) - 44 + 2q + color(red)(6q)#

#64 - 0 = 0 + (2 + color(red)(6))q#

#64 = 8q#

#64/color(red)(8) = (8q)/color(red)(8)#

#8 = (color(red)(cancel(color(black)(8)))q)/cancel(color(red)(8))#

#8 = q#

#q = 8#

*Step 3) Substitute #8# for #q# in the solution to either equation in Step 1 and calculate #p#:

#4p = 20 - 6q# becomes:

#4p = 20 - (6 * 8)#

#4p = 20 - 48#

#4p = -28#

#(4p)/color(red)(4) = -28/color(red)(4)#

#(color(red)(cancel(color(black)(4)))p)/cancel(color(red)(4)) = -7#

#p = -7#

The Solution Is: #p = -7# and #q = 8#