Find the largest and smallest value of the function f (x) = x ^ 4 -2x on the segment [0.3].
September 7, 2021 | education
| Given a function:
f (x) = x ^ 4 – 2x;
Let’s find the derivative of this function:
f ‘(x) = 4 * x ^ 3 – 2 * 1 = 4x ^ 3 – 2.
Let’s find the zeros of this derivative on the graphs, equating it to zero:
4x ^ 3 – 2 = 0;
4x ^ 3 = 2;
x ^ 3 = 2/4;
x = ^ 3√2/4.
Now let’s substitute this value into the function:
f (^ 3√ 2/4) = (^ 3√ 2/4) ^ 4 – 2 * ^ 3√ 2/4 = – (3 * ^ 3√ 4) / 4 ~ (approximately equal) ~ -1.2.
Substitute the extreme points of the segment that this function belongs to:
f (0) = 0 ^ 4 – 2 * 0 = 0 – 0 = 0.
f (3) = 3 ^ 4 – 2 * 3 = 81 – 6 = 75.
Thus, the smallest value of this function on the segment [0; 3]: -1.2.
And the largest value of the function on the segment [0; 3] = 75.
Answer: highest value: 75; smallest value: -1.2.
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