(9x^4-13x^3-x-7)+(7x^3-2x+1)=
9x^4-13x^3-x-7+7x^3-2x+1=
9x^4+(-13+7)x^3+(-1-2)x-7+1=
9x^4+(-6)x^3+(-3)x-6=
9x^4-6x^3-3x-6
Answer: Option <span>D.)9x^4−6x^3−3x−6</span>
For the X intercept you set y = 0 and solve for x
Y =

x + 9
0=

x + 9 subtract 9 from both sides
-9 =

divide both sides by 3
-3 = -8x divide both sides by -8

= x
X-intercept = (

, 0)
<u>End behavior: </u>
The parent function is: f(x) = x³, which starts (from the left side) at -∞ and ends (on the right side) at +∞.
<u>Zeroes:</u>
f(x) = x³ + 2x² - 8x
0 = x³ + 2x² - 8x
0 = x(x² + 2x - 8)
0 = x(x + 4)(x - 2)
0 = x 0 = x + 4 0 = x - 2
x = 0 x = -4 x = 2
<u>Intervals:</u>
Put the zeroes in order: -4, 0, 2
since f(x) is increasing from the left then the interval from -4 to 0 is positive and the interval from 0 to 2 is negative.
<u>Graph:</u>
see attachment
See image that is attached.