Maths Methods

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Ellis

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Sep 2, 2020
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Hi everyone, I really need some help with this question please?
For the equation y=ax^3+bx^2+cx+d
show that a=0.05,
b=-4.25,
c=120,
and d=-1125,
when y=0, x=25
y=0, x= 30,
and when y=36/5, x=34
 
Ellis said:
Hi everyone, I really need some help with this question please?
For the equation y=ax^3+bx^2+cx+d
show that a=0.05,
b=-4.25,
c=120,
and d=-1125,
when y=0, x=25
y=0, x= 30,
and when y=36/5, x=34
Click to expand...
Please show us what you have tried and exactly where you are stuck.

Please follow the rules of posting in this forum, as enunciated at:


Please share your work/thoughts about this problem.
 
For this question I have tried substituting the coordinates into the equation to find the values of abc and d, however I don’t know how to cancel any more out
 
Ellis, the method you have used seems correct. Usually when you have 4 unknowns, as you do here, you need 4 equations to solve them.
Is there any other information you were given? Could you please post the question EXACTLY as it was given to you?
The only other thing you can do is write the quartic with the values of a,b,c,and d since they are given, and verify that the points satisfy that equation.
 
There needs to be one more equation so that you can get the values listed.
I am more concerned that you said that you are having trouble canceling out. I assume that you mean to solve for some of the unknowns.
It is extremely hard to help you if you do not explain why you can't go any further. What methods have you learned? Which method do you want to use? There are a few ways to solve this (once you give us the last equation) but we need to know how you want to proceed so that we can help you.
 
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