Finding Constants for Quadratic Equations

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SUMMARY

The discussion focuses on finding constants P, Q, R, S, a, and b that satisfy the equations P(x-a)2 + Q(x-b)2 = 5x2 + 8x + 14 and R(x-a)2 + S(x-b)2 = x2 + 10x + 7. Participants confirmed the correctness of the proposed solutions, emphasizing the importance of algebraic manipulation and understanding of quadratic forms. The discussion highlights the necessity of equating coefficients to derive the constants accurately.

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anemone
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Find constants $P,\,Q,\,R,\,S, a,\,b$ such that

$P(x-a)^2+Q(x-b)^2=5x^2+8x+14$

$R(x-a)^2+S(x-b)^2=x^2+10x+7$
 
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anemone said:
Find constants $P,\,Q,\,R,\,S, a,\,b$ such that

$P(x-a)^2+Q(x-b)^2=5x^2+8x+14$

$R(x-a)^2+S(x-b)^2=x^2+10x+7$
compare both sides we get:
$P+Q=5---(1)$
$aP+bQ=-4---(2)$
$a^2P+b^2Q=14---(3)$
$R+S=1---(4)$
$aR+bS=-5---(5)$
$a^2R+b^2S=7---(6)$
from (1)(2)(3) we get :
$-b=\dfrac {14+4a}{5a+4}---(7)$
from (4)(5)(6) we get :
$-b=\dfrac {7+5a}{a+5}--(8)$
from (7)(8) we get :
$a=-2,1$
the rest is easy ,and the solutions will be:
$(a,b,P,Q,R,S)=(-2,1,3,2,2,-1)$
or:
$(a,b,P,Q,R,S)=(1,-2,2,3-1,2)$
 
Thanks for participating, Albert and your answer is correct!:)
 

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