SOLUTION: The number x satisfies 5x^2 + 4 = 3x + 9. Find the value of (10x

SOLUTION: The number x satisfies 5x^2 + 4 = 3x + 9. Find the value of (10x - 3)^2.

Question 1086050: The number x satisfies 5x^2 + 4 = 3x + 9. Find the value of (10x - 3)^2.
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
rewrite as 5x^2-3x-5=0
x=(1/10)(3+/- sqrt (9+100); sqrt 109=10.44
x=(1/10)13.44=1.34; exact answer is {3+sqrt(109)}/10
x=(1/10)(-7.44)=-0.74 exact answer is {3-sqrt(109)}/10
check
8.98+4=4.02+9 within rounding error.
6.74=-2.22+9, same

10x=3+sqrt(109) and 3-sqrt(109)
(10x-3)^2=9+6 sqrt(109)+109=118+6 sqrt(109)
(10x-3)^2=9-6 sqrt(109)+109=118-6 sqrt(109)

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