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Mathematics 21 Online
OpenStudy (anonymous):

According to the FTA theorem, this equation has how many solutions? x^3 + 4x^2 – 75 = 0

ganeshie8 (ganeshie8):

whats the degree of equation ?

OpenStudy (anonymous):

What do you mean by degree?

ganeshie8 (ganeshie8):

degree or order, they mean the same

ganeshie8 (ganeshie8):

they mean, highest exponent

OpenStudy (anonymous):

3

ganeshie8 (ganeshie8):

correct :D

OpenStudy (anonymous):

So that's the answer?

OpenStudy (anonymous):

Wow...that's more simple than I expected.

ganeshie8 (ganeshie8):

FTA says, if an equation has a degree of 3, then it will have exactly 3 solutions

ganeshie8 (ganeshie8):

if an equation has a degree of 100, then it wll have exactly 100 solutions

ganeshie8 (ganeshie8):

more generally, we say : if an equation has a degree of \(\textbf{n}\), then it will have exactly \(\textbf{n}\) solutions.

OpenStudy (anonymous):

Could you help me find the three solutions?

ganeshie8 (ganeshie8):

i dont think so, it looks complicated to work analytically using Rational Roots & Descartes rule of signs.

OpenStudy (anonymous):

oh :(

ganeshie8 (ganeshie8):

this particular equation, as i dont see any rational roots that satisfy this equation

OpenStudy (anonymous):

Can you tell me what type of function this is?

ganeshie8 (ganeshie8):

we can call it a cubic function

ganeshie8 (ganeshie8):

since it has a degree of 3

OpenStudy (anonymous):

Could I graph it without finding the solutions?

ganeshie8 (ganeshie8):

do u have geogebra ?

OpenStudy (anonymous):

I could get it? Could I find the solutions with the program?

ganeshie8 (ganeshie8):

here you may see the graph : http://www.wolframalpha.com/input/?i=x%5E3+%2B+4x%5E2+%E2%80%93+75+%3D+0

ganeshie8 (ganeshie8):

but ur teacher wont give u marks if u dont show the work

ganeshie8 (ganeshie8):

clearly it doesnt have any rational solutions,

OpenStudy (anonymous):

I know. I just don't know how to do it. I'm homeschooled...so it's difficult to understand the work.

ganeshie8 (ganeshie8):

it has 1 real solution , and 2 complex solutions

ganeshie8 (ganeshie8):

i get u, this particular equation is very tough, ask ur teacher only in DBA how to go about solving this problem :)

OpenStudy (anonymous):

Okay, thank you..

ganeshie8 (ganeshie8):

good luck !

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