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#1 2018-03-18 04:34:43
- Monox D. I-Fly
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[ASK] Integral
The area of the region limited by the curve [MATH]y=x^2+2x-3[/MATH], X-axis, Y-axis, and the line x = 2 is ....
A. 4 area unit
B. 9 area unit
C. 11 area unit
D. 13 area unit
E. 27 area unit
My attempt so far:
(x + 3)(x - 1) = 0
x = -3 or x = 1
X-intercept is at x = -3 and x = 1.
After drawing the graph, the restriction is x = 1 to x = 2.
Where did I do wrong? I know from the graph that the answer is A since the area covered is less large than a [MATH]1\times5[/MATH] rectangle and the option A is the only one with a value less than 5, but what did I do wrong algebraically?
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#2 2018-03-18 04:54:32
Re: [ASK] Integral
In particular, the second pair of brackets in the second line and the first pair of brackets in the third line are not correct.
However, the question appears to be badly worded. The area 'bounded' by the curve, the axes and the line x = 2 is not bounded at all -- it is infinite.
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#3 2018-03-18 05:24:17
- Monox D. I-Fly
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Re: [ASK] Integral
Then, do you think it has no answer?
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#5 2018-03-18 06:54:03
- Alg Num Theory
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Re: [ASK] Integral
The question as it stands has no answer (the area would be infinite). There is probably a typo in the question.
The question makes perfect sense and there is a perfectly good answer.
So, noting that the function is negative between 0 and 1 and positive between 1 and 2, the area should be
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Last edited by Alg Num Theory (2018-03-18 06:58:10)
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#6 2018-03-18 11:50:58
- Monox D. I-Fly
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Re: [ASK] Integral
darn, I forgot that it doesn't have to be in the first quadrant. Thanks Alg Num Theory.
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May his adventurous soul rest in peace at heaven.
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#7 2018-03-18 21:31:39
- Alg Num Theory
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Re: [ASK] Integral
Any time. 
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