Polynomials Question (1 Viewer)

[Ostentatious]

My working out is too muddled up to post here, I keep ending up with quadratics that I can't solve.

Ex 27(d) Q8 Fitzpatick 3U: Solve the equation 4x³ + 32x² + 79x + 60 = 0 given that one root is equal to the sum of the other two.

 

[shaon0]

My working out is too muddled up to post here, I keep ending up with quadratics that I can't solve.

Ex 27(d) Q8 Fitzpatick 3U: Solve the equation 4x³ + 32x² + 79x + 60 = 0 given that one root is equal to the sum of the other two.

Let roots be; a,b,a+b
Sum of roots: 2a+2b = (-8)
a+b=-4......1 => a=-4-b
Product of roots:
ab(a+b)=-15.....2
sub 1 into 2.
Thus, ab=(15/4)....3
sub 1 into 3.
(-4-b)b=(15/4)
b^2+4b+(15/4)=0
b{1,2} = (-4+-sqrt(16-15))/2
b{1} = -1.5, b{2}=-2.5
Thus, a=-2.5, -1.5.
Thus, x= -2.5, -1.5, -4.

 

[Aquawhite]

The day I actually get to reply to one of the maths forums with my answer being first will be a miracle XD

 

[Timothy.Siu]

The day I actually get to reply to one of the maths forums with my answer being first will be a miracle XD

yeah first u have to know how to do them

 

[gurmies]

yeah first u have to know how to do them

xD