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D( x )
(0.3-x)*(0.4-x) = 0
(0.3-x)*(0.4-x) = 0
(0.3-x)*(0.4-x) = 0
( 0.3-x )
0.3-x = 0 // - 0.3
-x = -0.3 // * -1
x = 0.3
( 0.4-x )
0.4-x = 0 // - 0.4
-x = -0.4 // * -1
x = 0.4
x in (-oo:0.3) U (0.3:0.4) U (0.4:+oo)
4.2 = x/((0.3-x)*(0.4-x)) // - x/((0.3-x)*(0.4-x))
4.2-(x/((0.3-x)*(0.4-x))) = 0
(-1*x)/((0.3-x)*(0.4-x))+4.2 = 0
(-1*x)/((0.3-x)*(0.4-x))+(4.2*(0.3-x)*(0.4-x))/((0.3-x)*(0.4-x)) = 0
4.2*(0.3-x)*(0.4-x)-1*x = 0
4.2*x^2-3.94*x+0.504 = 0
4.2*x^2-3.94*x+0.504 = 0
4.2*x^2-3.94*x+0.504 = 0
DELTA = (-3.94)^2-(0.504*4*4.2)
DELTA = 3.94^2-8.4672
DELTA = 7.0564
DELTA > 0
x = ((3.94^2-8.4672)^(1/2)+3.94)/(2*4.2) or x = (3.94-(3.94^2-8.4672)^(1/2))/(2*4.2)
x = 0.11904762*((3.94^2-8.4672)^(1/2)+3.94) or x = 0.11904762*(3.94-(3.94^2-8.4672)^(1/2))
(x-0.11904762*(3.94-(3.94^2-8.4672)^(1/2)))*(x-0.11904762*((3.94^2-8.4672)^(1/2)+3.94)) = 0
((x-0.11904762*(3.94-(3.94^2-8.4672)^(1/2)))*(x-0.11904762*((3.94^2-8.4672)^(1/2)+3.94)))/((0.3-x)*(0.4-x)) = 0
((x-0.11904762*(3.94-(3.94^2-8.4672)^(1/2)))*(x-0.11904762*((3.94^2-8.4672)^(1/2)+3.94)))/((0.3-x)*(0.4-x)) = 0 // * (0.3-x)*(0.4-x)
(x-0.11904762*(3.94-(3.94^2-8.4672)^(1/2)))*(x-0.11904762*((3.94^2-8.4672)^(1/2)+3.94)) = 0
( x-0.11904762*((3.94^2-8.4672)^(1/2)+3.94) )
x-0.11904762*((3.94^2-8.4672)^(1/2)+3.94) = 0 // + -0.11904762*((3.94^2-8.4672)^(1/2)+3.94)
x = -(-0.11904762*((3.94^2-8.4672)^(1/2)+3.94))
x = 0.11904762*((3.94^2-8.4672)^(1/2)+3.94)
( x-0.11904762*(3.94-(3.94^2-8.4672)^(1/2)) )
x-0.11904762*(3.94-(3.94^2-8.4672)^(1/2)) = 0 // + -0.11904762*(3.94-(3.94^2-8.4672)^(1/2))
x = -(-0.11904762*(3.94-(3.94^2-8.4672)^(1/2)))
x = 0.11904762*(3.94-(3.94^2-8.4672)^(1/2))
x in { 0.11904762*((3.94^2-8.4672)^(1/2)+3.94), 0.11904762*(3.94-(3.94^2-8.4672)^(1/2)) }
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