How do you solve the system 2p - 5q = 142p5q=14 and p + 3/2 q = 5p+32q=5?

1 Answer
Aug 21, 2017

See a solution process below:

Explanation:

Step 1) Solve each equation for 2p2p:

Equation 1

2p - 5q = 142p5q=14

2p - 5q + color(red)(5q) = 14 + color(red)(5q)2p5q+5q=14+5q

2p - 0 = 14 + 5q2p0=14+5q

2p = 14 + 5q2p=14+5q

Equation 2

p + 3/2q = 5p+32q=5

p + 3/2q - color(red)(3/2q) = 5 - color(red)(3/2q)p+32q32q=532q

p + 0 = 5 - 3/2qp+0=532q

p = 5 - 3/2qp=532q

color(red)(2) xx p = color(red)(2)(5 - 3/2q)2×p=2(532q)

2p = (color(red)(2) xx 5) - (color(red)(2) xx 3/2q)2p=(2×5)(2×32q)

2p = 10 - 3q2p=103q

Step 2) Substitute 10 - 3q103q from the second equation for 2p2p in the first equation and solve for pp:

2p = 14 + 5q2p=14+5q becomes:

10 - 3q = 14 + 5q103q=14+5q

-color(blue)(14) + 10 - 3q + color(red)(3q) = -color(blue)(14) + 14 + 5q + color(red)(3q)14+103q+3q=14+14+5q+3q

-4 - 0 = 0 + (5 + color(red)(3))q40=0+(5+3)q

-4 = 8q4=8q

-4/color(red)(8) = (8q)/color(red)(8)48=8q8

-1/2 = (color(red)(cancel(color(black)(8)))q)/cancel(color(red)(8))

-1/2 = q or q = -1/2

Step 3) Substitute -1/2 for q in either of the equations from Step 1 and calculate p:

2p = 14 + 5q becomes:

2p = 14 + (5 * -1/2)

2p = 14 - 5/2

2p = (2/2 * 14) - 5/2

2p = 28/2 - 5/2

2p = 23/2

color(red)(1/2) * 2p = color(red)(1/2) * 23/2

1p = 23/4

p = 23/4

The Solution Is: p = 23/4 and q = -1/2