help with finding x intercept of x^3 + 7x^2- 49x- 30

What is the x intercept of x^3 + 7x^2- 49x- 30?

jessica716 said:

What is the x intercept of x^3 + 7x^2- 49x- 30?

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I will guess that you mean "y = x[sup:aylp26gh]3[/sup:aylp26gh] + 7x[sup:aylp26gh]2[/sup:aylp26gh] - 49x - 30"...?

To find the x-intercept(s), plug zero in for y, and solve. For this equation, of course, you'll need to apply the Rational Roots Test, and then test the potential zeroes using synthetic division. :idea:

If you get stuck, please reply showing all of your work and reasoning. Thank you!

Eliz.

jessica716 said:

What is the x intercept of x^3 + 7x^2- 49x- 30?

Click to expand...

Did you put this into a graphing calculator?
That would give you some idea bout the approximate roots.

Mmm ... I think there are...

[attachment=0:29ugq3he]graph.jpg[/attachment:29ugq3he]

Using Newton-Raphson - I got these roots:

\(\displaystyle X_1 = 4.722109961\)

\(\displaystyle X_2 = -0.569658825\)

\(\displaystyle X_3 = -11.15245114\)

Does not look too rational to me - any one one of those!!