Functions doubt

In the line I have highlighted, why did we assume the leading coefficient of the quadratic to be greater than zero?
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13 Replies
iTeachChem Helper
@Apu
iTeachChem Helper
Note for OP
+solved @user1 @user2... to close the thread when your doubt is solved. Mention the users who helped you solve the doubt. This will be added to their stats.
iTeachChem
iTeachChem4mo ago
try visualising on a graph? the graph wont cut the x axis :)
Fusion
FusionOP4mo ago
Ye it won't cut if the leading coefficient (x^2 ka coefficient) is greater than zero Why is it greater than zero in this case? That's the part I'm confused on I understand the result applied although don't applied how the conditions of the result are met
CertifiedBrownMunda
Because thats the way we get an upward parabola and you need the quadratic to be greater than pr equal to zero hence a>0 is the only option
Fusion
FusionOP4mo ago
What if the coefficient was negative ? Can D somehow be less than zero in that case?
CertifiedBrownMunda
y=ax^2+bx+c is an equation of parabola on y axis with two possible orientations. Upward opening and downward opening. A layman explanation without hardcore proof is that Since x^2 will grow faster than the linear part, the coefficient of x^2 determines the sign at a point more or less. So for upward opening and positive values a should be greater D depends on values of a,b,c. D can be less than zero in case a is negative too But then the parabola will be downward facing without ever intersecting the x axis Which means the quadratic will always have a negative value But we dont want that right? We want greater than 0 values D describes whether the quadratic will have any roots or not. Coefficient determines how the parabola will behave at infinity Together D and a defines whether the quadratic will be always positive or always negative
Fusion
FusionOP4mo ago
Oh alright Thanks
CertifiedBrownMunda
You sure you understood the point?
Fusion
FusionOP4mo ago
Yup :D Sawal karte karte brain fuse ho gya tha Aapne basics yaad dilaye toh samaj aa gya
CertifiedBrownMunda
Cool. Mark it as solved as mentioned here
Fusion
FusionOP4mo ago
+solved @Satya S
iTeachChem Helper
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