Two Truths and a Lie - Mathematics

For each question, you are given three math-related statements and... STOP IT! An evil demon has manipulated them so now there's a false statement in every question! Can you identify each false statement?
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Last updated: April 2, 2022
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First submittedMarch 24, 2022
Times taken33
Average score60.0%
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1. Which statement is false?
The sum of a geometric series is given by the formula: S = a / (1 − r)
If n is odd, then n2 must be odd
If y = kx for some constant k, then dy/dx = k
The sum to infinity of a convergent geometric series is given by the formula S = a / (1 − r); the sum of the first n terms of a geometric series is given by S = a(1 − rn) / (1 − r) or S = a(rn − 1) / (r − 1)
2. Which statement is false?
The following identity is always true: sin(A + B) = sin A + sin B
The distributive property of multiplication is: a(b + c) = ab + ac
The Pythagorean theorem states that: a2 + b2 = c2
sin(A + B) = sin A cos B + cos A sin B
3. Which statement is false?
If f'(x) = 0 for some value of x, then (x,f(x)) must be the maximum point of the curve
If y = sin x, then dy/dx = cos x
The graph of y = 1 / x has asymptotes at the coordinate axes
It could be the local maximum point or the local minimum point, not necessarily the maximum point
4. Which statement is false?
The graph of y = f(x + 3) is a translation of the graph of y = f(x) 3 units to the left
All angles in a quadrilateral must be smaller than 180°
The slope of a line is given by the formula: m = (y2 − y1) / (x2 − x1)
Not necessarily; one of the angles could be reflex
5. Which statement is false?
(a + b)2 = a2 + b2
The following identity is always true: logab = 1 / logba (a≠1, b≠1)
Any non-zero number raised to the power of zero is 1
(a + b)2 = a2 + 2ab + b2
6. Which statement is false?
The power of a power rule is: (am)n = am + n
The identity sin2x + cos2x = 1 is true for all values of x
The modulus of vector x = 3i + 4j is 5
The power of a power rule should be: (am)n = amn
7. Which statement is false?
The graph of y = 2x + 1 meets the x-axis at the point (−½,0)
Euler's identity states that: e + 1 = 0
The following sequence is arithmetic: 1, 3, 6, 10, ...
The difference between two consecutive terms in an arithmetic sequence must be equal
8. Which statement is false?
The binomial expansion of (x + 1)3 is: x3 + 3x2 + 3x + 1
The power of a product rule is: (ab)n = anbn
The quadratic equation x2 − 2x − 3 = 0 has only one solution
Calculating the discriminant of the equation: b2 − 4ac = (−2)2 − 4(1)(−3) = 4 + 12 = 16 > 0, so there are two solutions
9. Which statement is false?
For all values of x, tan x = sin x / cos x
The only prime number that is also an even number is 2
For all values of x, sin 2x = 2 sin x cos x
tan x is undefined when cos x = 0 (i.e. when x = 90°, 270°, ...)
10. Which statement is false?
When converting degrees to radians, you divide by (360/π)
The formula used to convert Celsius temperatures into Fahrenheit, F = 1.8C + 32, is a linear function
The Greek letter Σ (sigma) is used to signify a sum
You should divide by (180/π)
1 Comments
+2
Level 76
Apr 2, 2022
The first question makes no sense. A series is an infinite sum. So the 'sum of a geometric series' does not mean anything.

Also if you say it's wrong because it's not specified that the series converges, then I would argue that e.g. the a, b and c in the Pythagorean theorem need to be specified before you could say it's correct.