Hi Pro35hp and MaxWong,
I think that you will both find this interesting. It ties in nicely with Alan's graph as well.
If you do not understand then please ask questions :)
x2+x+32x2+x−6≥0x2+x+32x2+4x−3x−6≥0x2+x+32x(x+2)−3(x+2)≥0x2+x+3(2x−3)(x+2)≥0 Now I will consider the numerator and put it equal yy=x2+x+3The discriminant is 12−12=−11 This means there are no real rootsSince the leading coefficiant is positive that means that y=x2+x+3is a concave up parabolaThis means that for all real values of x the numerator will be positive soIf the denominator is > or = zero the statement will be true.Truewhen(2x−3)(x+2)≥0If I graph y=(2x−3)(x+2)then this will be true when y is on or above the x axis, that is when y≥0 This is a concave up parabola so it will be true at the two endsroots are x=3/2and x=−2So the original statement will be true when x≤−2andwhenx≥1.5
Guest , also
I know that the up side is always true , because a>0 , and b^2-4ac<0
2x^2+x-6 can be expressed as (2x-3)(x+2)
x^2+x+3>0 is always true
(2x-3)(x+2)>=0 solution is (-inf;-2] U [3/2;+inf)
but (2x-3)(x+2) is down so we will eliminate -2 and 3/2
the final solution (-inf;-2) U (3/2;+inf)
this is the final answer
x2+x+32x2+x−6⩾0
x2+x+3⩾0
x⩾−1±√12−4(1)(3)2(1)
And the right hand side is imaginary.
yeah , my problem is that I can't express words in english .
so in writings problems I use their sentences lol
my level in english is not good enough
Hi Pro35hp and MaxWong,
I think that you will both find this interesting. It ties in nicely with Alan's graph as well.
If you do not understand then please ask questions :)
x2+x+32x2+x−6≥0x2+x+32x2+4x−3x−6≥0x2+x+32x(x+2)−3(x+2)≥0x2+x+3(2x−3)(x+2)≥0 Now I will consider the numerator and put it equal yy=x2+x+3The discriminant is 12−12=−11 This means there are no real rootsSince the leading coefficiant is positive that means that y=x2+x+3is a concave up parabolaThis means that for all real values of x the numerator will be positive soIf the denominator is > or = zero the statement will be true.Truewhen(2x−3)(x+2)≥0If I graph y=(2x−3)(x+2)then this will be true when y is on or above the x axis, that is when y≥0 This is a concave up parabola so it will be true at the two endsroots are x=3/2and x=−2So the original statement will be true when x≤−2andwhenx≥1.5
Melody's answer should be: x < -2 and x > 3/2
See the graph, here : https://www.desmos.com/calculator/afq8ukmpam