Evaluate: -3 + 5 - 8
- 6
- -10
- -6 Correct answer.
- 0
Explanation
Work left to right: -3 + 5 = 2, then 2 - 8 = -6. The result is negative because the final subtraction exceeds the running total.
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Work left to right: -3 + 5 = 2, then 2 - 8 = -6. The result is negative because the final subtraction exceeds the running total.
First (-2)^3 = -8. Then (-8) × (-3) = 24. A negative times a negative is positive, so the product is positive 24.
sqrt(144) = 12 and sqrt(64) = 8, so 12 - 8 = 4. Square roots are evaluated first, then subtracted.
Using the law of exponents, 2^3 × 2^2 = 2^(3+2) = 2^5 = 32. Equivalently, 8 × 4 = 32.
First simplify the parentheses: -2 + 4 = 2. Then -5 × 2 = -10. The single negative sign makes the product negative.
Using FOIL: x·x = x^2, x·(-2) = -2x, 3·x = 3x, 3·(-2) = -6. Combining -2x + 3x = x, so the result is x^2 + x - 6.
We need two numbers whose product is +12 and whose sum is -7. Those numbers are -3 and -4, so x^2 - 7x + 12 = (x - 3)(x - 4).
Substituting: 3^2 - 2(3)(1) + 1^2 = 9 - 6 + 1 = 4. Notice this equals (a - b)^2 = (3 - 1)^2 = 4.
First simplify sqrt(8) = sqrt(4·2) = 2*sqrt(2). Then 3*sqrt(2) + 2*sqrt(2) = 5*sqrt(2). Like radicals are combined just like like terms.
Using (a - b)^2 = a^2 - 2ab + b^2: (2x)^2 - 2(2x)(3) + 3^2 = 4x^2 - 12x + 9. The middle term is twice the product, with a negative sign.
This is a difference of squares: a^2 - b^2 = (a - b)(a + b). With a = x and b = 3, x^2 - 9 = (x - 3)(x + 3).
Using the difference of squares a^2 - b^2 = (a + b)(a - b) with a = x + 2 and b = x - 2: the sum is 2x and the difference is 4, so the product is 2x × 4 = 8x. Alternatively, expanding gives (x^2 + 4x + 4) - (x^2 - 4x + 4) = 8x.
Use the product property of radicals: sqrt(50) × sqrt(8) = sqrt(50 × 8) = sqrt(400) = 20. Alternatively, sqrt(50) = 5*sqrt(2) and sqrt(8) = 2*sqrt(2), so 5*sqrt(2) × 2*sqrt(2) = 10 × 2 = 20.
Subtract 5 from both sides: 2x = 6. Then divide by 2: x = 3. Check: 2(3) + 5 = 11.
First distribute: 3x - 6 = 9. Then add 6: 3x = 15. Divide by 3: x = 5. Alternatively, divide both sides by 3 first: x - 2 = 3, so x = 5.
Add the two equations: (x + y) + (x - y) = 7 + 1, so 2x = 8 and x = 4. Substitute back: 4 + y = 7, so y = 3.
Factor: x^2 - 5x + 6 = (x - 2)(x - 3) = 0. Setting each factor to zero gives x = 2 or x = 3. Check: 2 + 3 = 5 and 2 × 3 = 6.
Subtract 3 from both sides: 2x <= 8. Then divide by 2 (positive, so the inequality direction is preserved): x <= 4.
Let p = pens, n = notebooks. Then p + n = 8 and 200p + 300n = 1900. Substituting p = 8 - n: 200(8 - n) + 300n = 1900, so 1600 + 100n = 1900, giving n = 3 and p = 5. Check: 5 + 3 = 8 and 1000 + 900 = 1900.
Subtract the second equation from the first: (2x + y) - (x + y) = 8 - 5, so x = 3. Substitute into x + y = 5: 3 + y = 5, so y = 2.
Using x = (-b ± sqrt(b^2 - 4ac)) / (2a) with a = 1, b = -4, c = 1: the discriminant is 16 - 4 = 12, so x = (4 ± sqrt(12)) / 2 = (4 ± 2*sqrt(3)) / 2 = 2 ± sqrt(3).
Divide both sides by -2. When dividing an inequality by a negative number, the direction reverses: x > -3. This sign reversal is the key step that is often missed.
The 80 km/h portion covers 80 × 2 = 160 km. The remaining distance is 220 - 160 = 60 km. At 60 km/h, the time is 60 / 60 = 1 hour.
Recognize the perfect square: x^2 + 6x + 9 = (x + 3)^2 = 0. Taking the square root gives x + 3 = 0, so x = -3 (a double root).
Substitute y = 2x - 1 into x + y = 5: x + (2x - 1) = 5, so 3x = 6 and x = 2. Then y = 2(2) - 1 = 3. Check: 2 + 3 = 5.
First spend on pens: 3 × 200 = 600 yen. Remaining: 1200 - 600 = 600 yen. Each notebook costs 150 yen, so 600 / 150 = 4 notebooks. The constraint is 'at least 3 pens', so buying exactly 3 pens maximizes the notebook budget.
By the zero product property, if (x - 1)(x + 3) = 0 then x - 1 = 0 or x + 3 = 0. So x = 1 or x = -3.
Factor: find two numbers whose product is -8 and sum is -2. Those are -4 and 2, so x^2 - 2x - 8 = (x - 4)(x + 2) = 0, giving x = 4 or x = -2.
From the second equation: x = y + 2. Substitute into the first: 3(y + 2) + 2y = 16, so 5y + 6 = 16, giving y = 2. Then x = 2 + 2 = 4.
Direct proportion means y = kx. Substituting y = 12 and x = 4: 12 = k × 4, so k = 3. This means y = 3x for all values.
First find k: y = k/x, so 6 = k/2, giving k = 12. Then with y = 3: 3 = 12/x, so x = 4. As x increases, y decreases, which is the hallmark of inverse proportion.
Substitute x = -1: y = 2(-1) + 3 = -2 + 3 = 1. The negative input produces a smaller output, but the y-intercept of 3 keeps it positive.
Slope m = (6 - 2)/(3 - 1) = 4/2 = 2. Using point-slope with (1, 2): y - 2 = 2(x - 1), so y = 2x. Check with (3, 6): 2(3) = 6.
Substitute x = 2 and y = 8: 8 = a(2^2) = 4a, so a = 2. The function is y = 2x^2, a parabola opening upward with vertex at the origin.
Substitute x = 3: y = -2(3^2) = -2(9) = -18. The negative coefficient means the parabola opens downward, so all outputs for nonzero x are negative.
When x = 1, y = 1. When x = 3, y = 9. The change is 9 - 1 = 8. Note this is not proportional: tripling x from 1 to 3 multiplies y by 9, not by 3.
Complete the square: y = x^2 - 4x = (x - 2)^2 - 4. The vertex is at (2, -4), and the axis of symmetry is the line x = 2. The parabola opens upward since the coefficient of x^2 is positive.
Set the two expressions equal: 2x = -x + 3, so 3x = 3 and x = 1. Then y = 2(1) = 2. The intersection point is (1, 2), which satisfies both equations.
Find k: y = kx, so 15 = 5k, giving k = 3. Then y = 3(8) = 24. Direct proportion means y scales linearly with x.
Set y = 7: 7 = 3x - 2, so 3x = 9 and x = 3. Check: 3(3) - 2 = 7.
If y = k/x and x becomes 2x, then y' = k/(2x) = (1/2)(k/x) = y/2. In inverse proportion, when one variable doubles, the other is halved, keeping the product xy = k constant.
Using y = mx + b: 5 = -2(1) + b, so b = 7. The equation is y = -2x + 7. Check: when x = 1, y = -2 + 7 = 5.
When x = 2, y = 3(4) = 12. When x = 4, y = 3(16) = 48. The change is 48 - 12 = 36. The rate of change of a quadratic function is not constant; it accelerates as x moves away from the vertex.
Slope m = (y2 - y1)/(x2 - x1) = (-3 - 3)/(2 - (-1)) = -6/3 = -2. The negative slope means the line descends as x increases.
First find a: 18 = a(9), so a = 2 and y = 2x^2. Then y(2) = 2(4) = 8. Because y scales with x^2, reducing x from 3 to 2 cuts y from 18 to 8, not by the same factor as x.
Both lines have slope 3 but different y-intercepts (1 and -2). Lines with the same slope and different intercepts are parallel and never intersect. The y-intercept difference means they are distinct, not the same line.
Complete the square: y = (x - 3)^2 - 4. Since (x - 3)^2 is always non-negative, the minimum occurs when (x - 3)^2 = 0, giving y = -4 at x = 3. The parabola opens upward, so this is a minimum.
Factor: x^2 - 5x + 6 = (x - 2)(x - 3) = 0. By the zero product property, x = 2 or x = 3. These are the x-intercepts of the parabola.
Using the linear relationship t = V/r: t = 300/50 = 6 minutes. The volume is directly proportional to time, so the graph is a straight line through the origin with slope 50.
The sum of angles in a triangle is 180 degrees. The third angle is 180 - 50 - 60 = 70 degrees. This is the triangle angle sum theorem.