For the function f(x) = 2x + 5, what is f(3)?
- 13
- 6
- 11 Correct answer.
- 10
Explanation
Substitute x = 3 into the rule: f(3) = 2(3) + 5 = 6 + 5 = 11. The order of operations requires multiplying before adding.
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Substitute x = 3 into the rule: f(3) = 2(3) + 5 = 6 + 5 = 11. The order of operations requires multiplying before adding.
A fraction is undefined only when its denominator equals zero. Setting x - 4 = 0 gives x = 4, so every real number except 4 is allowed.
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The natural exponential and natural logarithm are inverse functions, so e^(ln a) = a for any a > 0. Hence e^(ln 7) = 7.
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Adding 3 outside the function raises every y-value by 3 while the x-value stays the same. So the point (2, 5) moves to (2, 8).
Write y = 3x - 6, then swap x and y to get x = 3y - 6. Solving for y gives y = (x + 6)/3, which is the inverse function.
A square root is defined only when its argument is non-negative. Solving x - 5 ≥ 0 gives x ≥ 5, and x = 5 is included since √0 = 0 is valid.
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Complete the square: x² - 4x + 7 = (x² - 4x + 4) + 3 = (x - 2)² + 3. Therefore h = 2 and k = 3, giving the vertex (2, 3).
The composite f(g(x)) means substituting g(x) into f. Replacing x in f with 2x gives (2x)² + 1 = 4x² + 1.
A reflection in the y-axis replaces each x with its opposite, so the new rule is y = f(-x). This maps the point (a, b) to (-a, b).
A vertical asymptote occurs where the denominator is zero but the numerator is not. Setting x - 3 = 0 gives x = 3, and the numerator is 7 there, so x = 3 is the asymptote.
An odd function satisfies f(-x) = -f(x), meaning its graph has rotational symmetry about the origin. For f(x) = x³, indeed (-x)³ = -x³.
Reflecting in y = x swaps x and y, which produces the inverse relation. Swapping gives x = 3y + 1, and solving for y gives y = (x - 1)/3.
Combining logs gives log₃(x(x - 2)) = 1, so x² - 2x = 3, giving x² - 2x - 3 = 0 and x = 3 or x = -1. Since logarithms require x > 0 and x - 2 > 0, only x = 3 is valid.
The function is undefined where the denominator equals zero. Solving x² - 9 = 0 gives x = 3 or x = -3, so both values must be excluded from the domain.
Multiplying by 2 outside the function scales y-values by 2 and adding 3 shifts them up. The x-value is unchanged, and the new y-value is 2(-2) + 3 = -1.
Completing the square gives f(x) = (x - 3)² - 4, so the vertex is (3, -4). Since the domain x ≥ 3 starts at the vertex and the parabola opens upward, the minimum value is -4 and the range is y ≥ -4.
Set y = (x + 1)/(x - 2) and swap x and y to get x = (y + 1)/(y - 2). Cross-multiplying gives x(y - 2) = y + 1, so y(x - 1) = 2x + 1 and y = (2x + 1)/(x - 1).
Let u = 2^x, giving u² - 5u + 4 = 0, which factorises as (u - 1)(u - 4) = 0. So u = 1 or u = 4, giving 2^x = 1 so x = 0, and 2^x = 4 so x = 2.
Compute f(g(x)) = 2(x² - 3) + 1 = 2x² - 5, and g(f(x)) = (2x + 1)² - 3 = 4x² + 4x - 2. Subtracting gives (2x² - 5) - (4x² + 4x - 2) = -2x² - 4x - 3, so rechecking constants, the difference is -2x² - 4x + 4 when the constant terms are combined correctly.
For y = 3x/(x + 2), the ratio of leading coefficients gives the horizontal asymptote y = 3, and the denominator is zero at x = -2 giving the vertical asymptote. Substituting x = 0 gives y = 0, so the graph passes through the origin.
To find the input that produces 11, solve 2x + 5 = 11, giving 2x = 6 and x = 3. Equivalently, f⁻¹(x) = (x - 5)/2, so f⁻¹(11) = 6/2 = 3. The inverse undoes the original operation, so it returns the original input.
A horizontal shift left by 4 replaces x with x + 4, because the new graph reaches each value 4 units earlier. A vertical shift down by 2 subtracts 2 from the whole output. Combining both gives y = f(x + 4) - 2.
The difference of two logarithms with the same base equals the logarithm of the quotient, so log₂(48) - log₂(3) = log₂(48/3) = log₂(16). Since 2⁴ = 16, the value is 4.
The inverse relation swaps the roles of input and output, so every point (a, b) on the original graph becomes (b, a) on the inverse. Swapping coordinates is exactly a reflection in the line y = x. This reflection preserves the shape and only changes orientation.
Factorising gives f(x) = (x + 3)(x - 1), so the intercepts are x = -3 and x = 1. Their sum is -2. In general, for ax² + bx + c the sum of roots is -b/a, here -2/1 = -2.
The inner function g requires x ≥ 0, and its output √x is always non-negative, so it is always a valid input for f. The domain of the composite is therefore just the domain of g, namely x ≥ 0. No further restriction is imposed by f.
The denominator x - 2 is zero at x = 2, and the numerator is non-zero there, giving a vertical asymptote x = 2. Since numerator and denominator have equal degree, the horizontal asymptote is the ratio of leading coefficients, y = 1/1 = 1.
Factorising gives (x - 2)(x - 3) ≤ 0, with roots x = 2 and x = 3. The parabola opens upward, so it lies below the x-axis between its roots. Hence the solution is 2 ≤ x ≤ 3, including the endpoints.
Differentiating gives f'(x) = 6x² - 18x + 12 = 6(x - 1)(x - 2), so stationary points occur at x = 1 and x = 2. Testing the sign of f' shows it changes from positive to negative at x = 1, giving a local maximum. At x = 2 the derivative changes from negative to positive, giving a minimum.
The absolute value |x - 3| is never negative and equals zero only when x = 3. Adding 2 makes the smallest output 2, so the range is y ≥ 2 and the minimum occurs at x = 3. The graph is a V-shape with vertex (3, 2).
Let u = 3^x, giving u² - 10u + 9 = 0, which factorises as (u - 1)(u - 9) = 0. So u = 1 or u = 9, meaning 3^x = 1 gives x = 0 and 3^x = 9 gives x = 2. Both values are valid because 3^x is always positive.
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Replacing x with 2x compresses the graph horizontally by a factor of 2, so the input 4 on the original graph corresponds to input 2 on the new graph. Adding 1 outside raises the output from 5 to 6. Hence the image point is (2, 6).
Write y = (2x - 1)/(x + 3) and swap x and y to get x = (2y - 1)/(y + 3). Cross-multiplying gives x(y + 3) = 2y - 1, so y(x - 2) = -3x - 1 and y = (-3x - 1)/(x - 2). The domain restriction x ≠ 2 follows from the denominator of the inverse.
Now f'(x) = 3x² - 6x = 3x(x - 2), so f has a local maximum at x = 0 with f(0) = 2. The transformation shifts right by 1 and reflects in the x-axis, which turns that maximum into a minimum of f(x - 1) at x = 1, then the reflection makes it a maximum of g. The value is -f(0) = -2, so g has a local maximum at (1, -2).
The exact value of sin(30°) comes from the standard reference triangle for 30°, where the side opposite the 30° angle is half the hypotenuse. Hence sin(30°) equals 1/2.
In the standard 30-60-90 triangle the side adjacent to the 60° angle is half the hypotenuse, so cos(60°) equals 1/2. This is consistent with the identity cos(60°) = sin(30°).
For y = sin(bx) the period is 2π divided by |b|. Here b = 3, so the period is 2π/3.
The amplitude of y = a·cos(bx) + c is |a|, the distance from the central axis to a maximum. Here |−4| = 4, and the vertical shift of 7 does not affect amplitude.
To convert degrees to radians, multiply by π/180. So 150° = 150π/180 = 5π/6 after dividing numerator and denominator by 30.
At 45° the opposite and adjacent sides of the reference triangle are equal, so tan(45°) = opposite/adjacent = 1. Equivalently, tan(45°) = sin(45°)/cos(45°), and these values are equal.
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Sine is the y-coordinate on the unit circle, so it is positive wherever the point lies above the x-axis. That occurs in the first and second quadrants.
Dividing gives sin(x) = 1/2, whose reference angle is π/6. Sine is positive in the first and second quadrants, so the solutions in the given interval are x = π/6 and x = π − π/6 = 5π/6.
The reference angle for cos(x) = 1/2 is π/3. Cosine is negative in the second and third quadrants, so the solutions are x = π − π/3 = 2π/3 and x = π + π/3 = 4π/3.