px2+3x+q=0 has two equal roots x=-1andx=-2 find p-q
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if x=-1
p(-1)^2 + 3(-1) +q=0
p-3+q=0
p+q=3------(1)
if x=-2,
p(-2)^2 +3(-2) + q=0
4p-6+q=0
4p+q=6------(2)
subtract (1)-(2).,,
p+q-4p-q=3-6
-3p=-3
p=1
substitute p=1 in (1)..,
1+q=3
q=3-1
q=2
therefore, p-q=1-2
=-1
p(-1)^2 + 3(-1) +q=0
p-3+q=0
p+q=3------(1)
if x=-2,
p(-2)^2 +3(-2) + q=0
4p-6+q=0
4p+q=6------(2)
subtract (1)-(2).,,
p+q-4p-q=3-6
-3p=-3
p=1
substitute p=1 in (1)..,
1+q=3
q=3-1
q=2
therefore, p-q=1-2
=-1
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