Tuesday

September 30, 2014

September 30, 2014

Posted by **rita** on Friday, July 22, 2011 at 9:34am.

pls help me i dont understand the question....

- math -
**Reiny**, Friday, July 22, 2011 at 10:45amdy/dx = 3x^2 + 1

at (1,4) , dy/dx = 4

tangent equation

4 = 4(1) + b

b = 0

the tangent equation at (1,4) is y = 4x

where does this cross or touch y = x^3 + x + 2 ?

x^3 + x + 2 = 4x

x^3 - 3x + 2 = 0

let f(x) = x^3 - 3x + 2

f(1) = 1 - 3 + 2 = 0 , so x-1) is a factor

by synthetic division ...

x^3 - 3x + 2 = (x-1)(x^2 + x - 2)

= (x-1)(x-1)(x+2)

then the roots of x^3 - 3x + 2 = 0 are

x = 1 and x = -1 and x = -2

we knew x = 1 from the tangent part, so the new x = -2 is the other intersection point value

if x = -2

y = -8 - 2 + 2 = -8

the other point is (-2,-8)

**Answer this Question**

**Related Questions**

Please check my maths? - How should i do this question?? it says: find the ...

math - the tangent yo the curve y=x^2 +5x -2 @ the point (1,4)intersect the ...

calculus - 1. Given the curve a. Find an expression for the slope of the curve ...

calculus - Consider the curve defined by 2y^3+6X^2(y)- 12x^2 +6y=1 . a. Show ...

Math - a curve is such that dy/dx=4x+7. the line y=2x meets the curve at point '...

Math - a curve is such that dy/dx=4x+7. the line y=2x meets the curve at point '...

math - find the eqt. of tangent to the curve y=-x^2+2x-10 @ the point where the ...

12th Grade Calculus - 1. a.) Find an equation for the line perpendicular to the ...

calculus - Consider the curve given by the equation y^3+3x^2y+13=0 a.find dy/dx...

calculus - A curve passes through the point (1,-11) and it's gradient at any ...