Please help with my math!!!
2 answers:
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Answer:
(-∞, -2), (-2, -0.618), and (1.618, 3)
Step-by-step explanation:
The red plus (+) signs indicate the regions in which the function is concave up, and the red negative (-) signs indicate the regions in which the function is concave down.
Note that the sign of the concavity changes at an inflection point.
Let's examine the intervals given.
(-∞, -2): Yes, concave up.
(-∞, -1.17): No. Concave up in (-∞, -2) but concave down in (-2, -1.17).
(-2, 0): No. Concave down in (-2, -1.17) but increasing in (-1.17, 0.0).
(-1.17, 0.689): Yes. Concave up.
(-0.618, 1.618): No. Concave up in (-0.618, 0.689) but concave down in (0.689, 1.618).
(0, 3): No. Concave up in (0, 0.689), concave down in (0.689, 2.481), and concave up in (2.481, 3).
(2.481, ∞): Yes. Concave up.
The three intervals that are concave up are (-∞, -2), (-1.17, -0.689), and (2.481, ∞).
Number of dimes were 81 and number of quarters were 47
<em><u>Solution:</u></em>
Let "d" be the number of dimes
Let "q" be the number of quarters
We know that,
value of 1 dime = $ 0.10
value of 1 quarter = $ 0.25
<em><u>Given that There are 128 coins in all</u></em>
number of dimes + number of quarters = 128
d + q = 128 ------ eqn 1
<em><u>Also given that collection of dimes and quarters is worth $19.85</u></em>
number of dimes x value of 1 dime + number of quarters x value of 1 quarter = 19.85
0.1d + 0.25q = 19.85 -------- eqn 2
<em><u>Let us solve eqn 1 and eqn 2</u></em>
From eqn 1,
d = 128 - q -------- eqn 3
<em><u>Substitute eqn 3 in eqn 2</u></em>
0.1(128 - q) + 0.25q = 19.85
12.8 - 0.1q + 0.25q = 19.85
12.8 + 0.15q = 19.85
0.15q = 7.05
<h3>q = 47</h3>Therefore from eqn 3,
d = 128 - q
d = 128 - 47
<h3>d = 81</h3>Thus number of dimes were 81 and number of quarters were 47