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Zorluk: ZorFunctions and Custom Symbol Operations

For any real number xx, the custom unary operation \triangle is defined by (x)=2xx2\triangle(x) = 2x - x^2. For all real numbers uu and vv, the custom binary operation \odot is defined by uv=(u)+(v)+uvu \odot v = \triangle(u) + \triangle(v) + uv. The function ff is defined for all real numbers xx by f(x)=x(3x)f(x) = x \odot (3 - x). What is the maximum value of f(x)f(x)?

Cevap: 3.75

Cevap

The maximum value of f(x)f(x) is 3.753.75 (or 154\frac{15}{4}).
Expanding f(x)=x(3x)f(x) = x \odot (3 - x) yields (x)+(3x)+x(3x)\triangle(x) + \triangle(3 - x) + x(3 - x). Substituting (t)=2tt2\triangle(t) = 2t - t^2 gives (2xx2)+(62x(96x+x2))+(3xx2)=3x2+9x3(2x - x^2) + (6 - 2x - (9 - 6x + x^2)) + (3x - x^2) = -3x^2 + 9x - 3. The vertex of this quadratic function occurs at x=96=1.5x = \frac{9}{6} = 1.5, where f(1.5)=3(2.25)+13.53=3.75f(1.5) = -3(2.25) + 13.5 - 3 = 3.75.

Adım Adım Çözüm

1
Evaluate the custom unary operation \triangle for each argument
(x)=2xx2\triangle(x) = 2x - x^2 and (3x)=2(3x)(3x)2=x2+4x3\triangle(3-x) = 2(3-x) - (3-x)^2 = -x^2 + 4x - 3
Substitute xx and 3x3-x into the definition (t)=2tt2\triangle(t) = 2t - t^2 and expand carefully.
2
Compute the product term uvuv
x(3 - x) = 3x - x^2
The binary definition uvu \odot v includes an additive product term uvuv.
3
Sum all components to construct the explicit quadratic expression for f(x)f(x)
f(x) = (2x - x^2) + (-x^2 + 4x - 3) + (3x - x^2) = -3x^2 + 9x - 3
Combine like terms for x2x^2, xx, and the constant.
4
Determine the vertex of the downward-opening parabola f(x)=3x2+9x3f(x) = -3x^2 + 9x - 3
x = \frac{3}{2} = 1.5 ,yielding, yielding f(1.5) = 3.75$
Since the coefficient of x2x^2 is negative (3<0-3 < 0), the maximum occurs at x=b2a=96=1.5x = -\frac{b}{2a} = \frac{9}{6} = 1.5.

Anahtar Kavram

Custom operations combined with quadratic function optimization
Tahmini Süre:2m 0s
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