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I don't understand what this math problem is asking for can someone help?
Consider the region bounded by the following graphs:
y = x^2 + 2x - 15, the x-axis, x=4 and x=7
what is the least number of integral needed to find the area of this region?
I have no idea what the question is asking can someone help or maybe give me steps. Thanks.
3 Answers
- az_lenderLv 75 days agoFavorite Answer
Only one integral is needed:
the integral from x = 4 to x = 7 of
(x^2 + 2x - 15) dx.
After integration you have
(1/3)x^3 + x^2 - 15x;
plug in x = 7 and x = 4, you get
(1/3)(343 - 64) + (49 - 16) - 15(7 - 4)
= (1/3)(279) + 33 - 45
= 81.
Do check my arithmetic.
- ?Lv 75 days ago
The wording of this question is very odd. If it's asking for the area of the region bounded by
y = x² + 2x - 15
x = 4
x = 7
This can be found by taking one integral:
₇ ₇
∫ x² + 2x - 15 dx = (⅓ x³ + x² - 15x ⃒
⁴ ⁴
= 58.33 - (-22.67)
= 81 ...................ANS
- billrussell42Lv 75 days ago
draw it out. from the graph, you want the area under y = x² + 2x - 15 from 3 to 7, one integration.
although that one integral is broken down into 3 using the rule ∫(a+b)du = ∫a du + ∫b du
A = ∫ (x² + 2x - 15) dx from 3 to 7
A = (1/3)x³ + x² – 15x from 3 to 7
A = (1/3)7³ + 7² – 15•7 – ((1/3)3³ + 3² – 15•3)
A = 343/3 + 49 – 105 – 9 – 9 + 45
A = 114 1/3 – 29 = 85 1/3
edit: missed the x= 4, but that just changes it a bit to
A = (1/3)x³ + x² – 15x from 4 to 7
A = (1/3)7³ + 7² – 15•7 – ((1/3)4³ + 4² – 15•4)
A = 343/3 + 49 – 105 – 64/3 – 16 + 60
A = 279/3 – 12 = 81