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If the slope of one of the lines given by ax2 + 2hxy + by2 = 0 is square of the slope of the other line, show that a2b + ab2 + 8h3 = 6abh. - Mathematics and Statistics

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प्रश्न

If the slope of one of the lines given by ax2 + 2hxy + by2 = 0 is square of the slope of the other line, show that a2b + ab2 + 8h3 = 6abh.

योग

उत्तर

Let m be the slope of one of the lines given by ax2 + 2hxy + by2 = 0. 
Then the other line has slope m2

∴ m + m2 = `(-2"h")/"b"`     ....(1) and 

(m)(m2) = `"a"/"b"`

i.e. m3 = `"a"/"b"`        ....(2)

∴ (m + m2)3 = m3 + (m2)3 + 3(m)(m2)(m + m2) .....[∵ (p + q)3 = p3 + q3 + 3pq(p + q)]

∴ `((- "2h")/"b")^3 = "a"/"b" + "a"^2/"b"^2 + 3"a"/"b"((-"2h")/"b")`

∴ `(-8"h"^3)/"b"^3 = "a"/"b" + "a"^2/"b"^2 - "6ah"/"b"^2`

Multiplying by b3, we get,

- 8h3 = ab2 + a2b - 6abh

∴ a2b + ab2 + 8h3 = 6abh

This is the required condition.

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Angle between lines represented by ax2 + 2hxy + by2 = 0
  क्या इस प्रश्न या उत्तर में कोई त्रुटि है?
अध्याय 4: Pair of Straight Lines - Miscellaneous Exercise 4 [पृष्ठ १३२]

APPEARS IN

बालभारती Mathematics and Statistics 1 (Arts and Science) [English] 12 Standard HSC Maharashtra State Board
अध्याय 4 Pair of Straight Lines
Miscellaneous Exercise 4 | Q 19 | पृष्ठ १३२

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