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Find the solution to the following A)p+2q-4=0 7p-q-3=0 by the substitution...
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High School Teacher
`1. p +2q - 4=0` and `2` . `7p-q-3=0`
There are 2 unknown variables (p and q) so convert the first equation `1.` to the form p= (or q= )
`p+2q -4=0` becomes `p= -2q +4`
and substitute into the other eequation:
`7p-q-3=0` becomes `7(-2q +4) -q -3 =0`
`therefore -14q+28 -q-3=0`
Note that the negative symbols cancel each other out.
Now solve for q by substituting into any one of your previous equations:
`therefore p= -2(5/3)+4`
`therefore p=-10/3 + 4`
`therefore p = 2/3`
(p;q): (`2/3; 5/3` )
To check substitute both values back into one of the equations. When both sides of the equation equal each other (LHS=RHS) ie left hand side equals right hand side, then the values are correct:
`7(2/3) - (5/3) - 3=0`
`14/3 -5/3 - 3 = 0`
`therefore 9/3-3 = 0`
Posted by durbanville on April 13, 2013 at 3:23 PM (Answer #1)
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