Calculate the value of (-6) + (+13) - (-5).
- 24
- 12 Correct answer.
- -12
- 2
Explanation
Subtracting a negative number becomes addition, so -(-5) = +5. The expression becomes -6 + 13 + 5. Computing from the left: -6 + 13 = 7, then 7 + 5 = 12.
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Subtracting a negative number becomes addition, so -(-5) = +5. The expression becomes -6 + 13 + 5. Computing from the left: -6 + 13 = 7, then 7 + 5 = 12.
Follow the order of operations. First (-4)² = 16, then 16 × 3 = 48, and 20 ÷ (-5) = -4. Finally, 48 - (-4) = 48 + 4 = 52.
Use the common denominator 15: 2/3 = 10/15 and 3/5 = 9/15. Then 10/15 - 9/15 = 1/15. The result is positive because 10/15 is larger than 9/15.
Substitute the values: 3(5) - 2(-2) = 15 - (-4). Subtracting a negative becomes addition, so 15 + 4 = 19.
Distribute: 4(x - 2y) = 4x - 8y and -3(x - 5y) = -3x + 15y. Combine like terms: (4x - 3x) + (-8y + 15y) = x + 7y.
Move the x terms to the left and constants to the right: 4x - 2x = -9 - 3, so 2x = -12. Dividing by 2 gives x = -6. Check: 4(-6) + 3 = -21 and 2(-6) - 9 = -21.
Add 1.2 to both sides: 0.3x = 2.1. Divide by 0.3: x = 2.1 ÷ 0.3 = 7. Multiplying both sides by 10 first (3x - 12 = 9) gives the same result.
Factor out the largest perfect square: 48 = 16 × 3, so √48 = √16 × √3 = 4√3. The radicand 3 has no perfect-square factors left.
Use √a × √b = √(ab): √3 × √27 = √(3 × 27) = √81 = 9. Alternatively, √27 = 3√3, so √3 × 3√3 = 3 × 3 = 9.
Taking square roots of both sides gives x = ±√36 = ±6. Both 6² = 36 and (-6)² = 36, so a positive number has two square roots, one positive and one negative.
Use the common denominator 6: [2(2x + 3y) - 3(x - y)]/6. Expand the numerator: 4x + 6y - 3x + 3y. Combine: x + 9y, so the result is (x + 9y)/6.
Use the expansion pattern (x + a)(x + b) = x² + (a + b)x + ab. Here a = 4 and b = -6, so a + b = -2 and ab = -24. The result is x² - 2x - 24.
Use (a + b)² = a² + 2ab + b² with a = 3x and b = 2. Then (3x)² = 9x², 2(3x)(2) = 12x, and 2² = 4. The result is 9x² + 12x + 4.
Find two numbers whose sum is +5 and product is -14: those are +7 and -2. So x² + 5x - 14 = (x + 7)(x - 2). Expanding confirms x² - 2x + 7x - 14 = x² + 5x - 14.
First factor out the common factor 2: 2(x² - 9). Then factor the difference of squares: x² - 9 = (x + 3)(x - 3). The complete factorization is 2(x + 3)(x - 3).
Add the two equations to eliminate y: 2x = 14, so x = 7. Substitute back: 7 + y = 10, so y = 3. Check in the second equation: 7 - 3 = 4.
From the second equation, x = y + 1. Substitute into the first: 2(y + 1) + 3y = 12, so 5y + 2 = 12 and y = 2. Then x = 2 + 1 = 3. Check: 2(3) + 3(2) = 12 and 3 - 2 = 1.
Let m be the mochi price and t the tea price. Then 2m + t = 700 and m + 2t = 500. Double the first equation: 4m + 2t = 1400. Subtract the second: 3m = 900, so m = 300. Check: t = 700 - 600 = 100, and 300 + 2(100) = 500.
Factor the left side: find two numbers with sum -5 and product +6, which are -2 and -3. So (x - 2)(x - 3) = 0, giving x = 2 or x = 3. Check: 2² - 5(2) + 6 = 0.
Find two numbers with sum +2 and product -8: those are +4 and -2. So (x + 4)(x - 2) = 0, giving x = -4 or x = 2. Check: 2² + 2(2) - 8 = 4 + 4 - 8 = 0.
The equation does not factor over integers, so use the quadratic formula: x = [4 ± √(16 - 4)]/2 = [4 ± √12]/2 = [4 ± 2√3]/2 = 2 ± √3. Dividing both terms of the numerator by 2 is the key final step.
Simplify each radical first: √12 = 2√3 and √27 = 3√3. Then 2√3 + 3√3 = 5√3, since like radicals combine in the same way as like terms.
Use the difference-of-squares pattern (a + b)(a - b) = a² - b². Here a² = (√5)² = 5 and b² = 4, so the result is 5 - 4 = 1. The middle terms -2√5 and +2√5 cancel.
Simplify each radical: √50 = 5√2 and √8 = 2√2. Then 5√2 - 2√2 = 3√2. Like radicals combine by subtracting their coefficients.
Multiply numerator and denominator by √3: 6/√3 = 6√3/(√3 × √3) = 6√3/3 = 2√3. Rationalizing removes the radical from the denominator.
Expand each part: (x + 3)(x - 3) = x² - 9 and (x - 2)² = x² - 4x + 4. Subtract: x² - 9 - (x² - 4x + 4) = x² - 9 - x² + 4x - 4 = 4x - 13. The x² terms cancel.
Use the identity (a + b)² = a² + 2ab + b², rearranged as a² + b² = (a + b)² - 2ab. Substitute: 6² - 2(4) = 36 - 8 = 28. This avoids needing to find a and b individually.
Expand the left side: x² - 2x + 1 = 2x + 6. Move everything to one side: x² - 4x - 5 = 0. Factor: (x - 5)(x + 1) = 0, so x = 5 or x = -1. Check x = 5: (5 - 1)² = 16 and 2(5) + 6 = 16.
Rewrite the expression using x - 1: x² - 2x + 3 = (x - 1)² + 2. Since x = √3 + 1, we have x - 1 = √3, so (x - 1)² = 3. The value is 3 + 2 = 5. Direct substitution gives the same result but with more work.
A proportional relationship has the form y = ax. From 12 = 4a, the constant is a = 3, so y = 3x. When x = 7, y = 3 × 7 = 21.
Inverse proportion means y = a/x with xy = a. From 6 = a/2, the constant is a = 12. When x = 4, y = 12/4 = 3. Doubling x halves y.
Substitute x = -3: y = 2(-3) - 5 = -6 - 5 = -11. Multiplying 2 by a negative x gives a negative product, which then combines with -5.
Slope = (change in y) ÷ (change in x) = (9 - 3)/(3 - 1) = 6/2 = 3. The y-values increase by 6 while the x-values increase by 2.
Speed = distance ÷ time = 240 ÷ 3 = 80 km/h. Distance traveled is proportional to time when the speed is constant, with the constant of proportionality equal to the speed.
Inverse proportion has the form y = a/x, equivalently xy = a, where a is a nonzero constant. The equation y = 12/x matches this form with a = 12: as x doubles, y halves.
Substitute x = -2: y = 3 × (-2)² = 3 × 4 = 12. The square of a negative number is positive, so y is positive whenever x is nonzero.
A line with slope 3 has the form y = 3x + b. Substitute the point (2, 5): 5 = 3(2) + b, so b = 5 - 6 = -1. The equation is y = 3x - 1. Check: at x = 2, y = 6 - 1 = 5.
Set the expressions equal: -x + 4 = 2x - 5, so 9 = 3x and x = 3. Then y = -3 + 4 = 1. The intersection is (3, 1). Check in the second line: 2(3) - 5 = 1.
Substitute the given point: -12 = a(2²) = 4a, so a = -3 and the function is y = -3x². At x = 3, y = -3 × 9 = -27.
The fare is a linear function: y = 100x + 500, where x is the distance in km. For x = 8, y = 100 × 8 + 500 = 800 + 500 = 1,300 yen.
For any linear function y = ax + b, the rate of change (change in y ÷ change in x) is always the slope a, regardless of the interval. Here a = -2. Verify: y goes from 5 to -1, a change of -6 over an x-change of 3, and -6 ÷ 3 = -2.
Compute the y-values: at x = -4, y = (1/2)(16) = 8; at x = -2, y = (1/2)(4) = 2. Rate of change = (2 - 8)/(-2 - (-4)) = -6/2 = -3. On the negative side of the parabola, y decreases as x increases toward 0.
The total supply is 40 × 12 = 480 sheets. Daily use and days lasted are inversely proportional, so at 30 sheets per day the supply lasts 480 ÷ 30 = 16 days.
Slope = (10 - 2)/(3 - (-1)) = 8/4 = 2. Using the point (3, 10): 10 = 2(3) + b, so b = 4. The equation is y = 2x + 4. Check the other point: 2(-1) + 4 = 2.
Substitute the point: 20 = a(-2)² = 4a, so a = 20 ÷ 4 = 5. Since (-2)² = 4 is positive and y = 20 is positive, a must be positive.
Let t be the hours elapsed. The length is y = 20 - 2t. Set 20 - 2t = 8, so 2t = 12 and t = 6. Check: after 6 hours, 20 - 12 = 8 cm remain.
The graph crosses the x-axis where y = 0. Set (3/2)x - 2 = 0, so (3/2)x = 2 and x = 2 × (2/3) = 4/3. The x-intercept is (4/3, 0).
The constant of proportionality is a = -15 ÷ 6 = -5/2, so y = (-5/2)x. When x = -8, y = (-5/2) × (-8) = 20. The product of two negatives is positive.
Set x² = x + 2, so x² - x - 2 = 0. Factor: (x - 2)(x + 1) = 0, giving x = 2 or x = -1. At x = 2, y = 4; at x = -1, y = 1. The points are (2, 4) and (-1, 1), and both satisfy the line equation too.
Because the domain includes x = 0, the minimum value of y is 2(0)² = 0, not the value at an endpoint. The maximum occurs at the endpoint farthest from 0: at x = 2, y = 2(4) = 8, while at x = -1, y = 2. So the range is 0 ≤ y ≤ 8.