Posted by **anonymous** on Thursday, April 17, 2008 at 6:07pm.

I need help solving this using the substitution method

4p-2q= 16,

5p + 7q= 1

- Math -
**amanda**, Thursday, April 17, 2008 at 6:15pm
19-7-5=

- Math -
**PsyDAG**, Thursday, April 17, 2008 at 7:56pm
Start with one formula.

4p - 2q = 16

Get one variable alone on one side of the equation.

-2q = 16 - 4p

q = 2p - 8

Then substitute the value into the other equation.

5p + 7q = 1

5p + 7(2p - 8)= 1

Solve for p.

Once you find p, put that value into the first equation to solve for q. To check, put both values back into the second equation.

I hope this helps. Thanks for asking.

- Math -
**Damon**, Thursday, April 17, 2008 at 8:07pm
4 p = 16 + 2 q

so

p = (4 + .5 q)

substitute that value for p in the second equation

5 (4 + .5 q) + 7 q = 1

20 + 2.5 q + 7 q = 1

9.5 q = -19

q = -190/95 = -38/19 =-2

put that back in either first or second equation to solve for p

p = 4 + .5*(-2)

p = 4 - 1 = 3

check

4(3) -2 (-2) = 12 + 4 = 16 check

5(3) + 7(-2) = 15 - 14 = 1 check

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