The line y = -6x-10 is tangent to the graph of the function y = x ^ 3 + 4x ^ 2-6x-10.
September 3, 2021 | education
| The line y = -6x-10 is tangent to the graph of the function y = x ^ 3 + 4x ^ 2-6x-10. Find the abscissa of the touch point.
y = kx + b – equation of a straight line;
y = -6x – 10; (1)
k = -6;
The slope of the tangent is equal to the tangent of the angle of inclination and is equal to the derivative at the point of tangency:
y ‘= tgх = k;
y ‘= -6;
y ‘= 3x ^ 2 + 8x – 6;
We equate and solve the equation:
3x ^ 2 + 8x – 6 = -6;
3x ^ 2 + 8x = 0;
x (3x + 8) = 0;
x = 0 or x = -8/3;
Substitute the obtained abscissas into the original function and into (1), choose the abscissa in which they are equal:
0 ^ 3 + 4 * 0 ^ 2 – 6 * 0 – 10 = -10;
-6 * 0 – 10 = -10;
Analytically, we see that at -8/3 they are not equal.
Answer: 0.
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