Algebra
- The expression x4 – 2x² + k will be a perfect square when the value of k is
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(a – b)² = a² –2ab + b²
x4– 2x² +k = (x²)² – 2.x2.1+ k
∴ k = (1)² = 1Correct Option: B
(a – b)² = a² –2ab + b²
x4– 2x² +k = (x²)² – 2.x2.1+ k
∴ k = (1)² = 1
- If x = ³√ a + √a² + b³ + ³√a - √a² + b³ , then x³ + 3bx is equal to
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x = ³√ a + √a² + b³ + ³√a - √a² + b³
Cubing both sides,
x³ = (³√ a + √a² + b³)³ + (³√a - √a² + b³)³ + (³√ a + √a² + b³)
(³√a - √a² + b³)(³√ a + √a² + b³ + ³√a - √a² + b³)
= a + √a² + b³ + a - √a² + b³ + 3 (a + √a² + b³ × a - √a² + b³)¹/3x
= 2a + 3(a² - a² - b³)¹/3x
= 2a + ( - 3bx)
∴ x³ + 3bx = 2aCorrect Option: C
x = ³√ a + √a² + b³ + ³√a - √a² + b³
Cubing both sides,
x³ = (³√ a + √a² + b³)³ + (³√a - √a² + b³)³ + (³√ a + √a² + b³)
(³√a - √a² + b³)(³√ a + √a² + b³ + ³√a - √a² + b³)
= a + √a² + b³ + a - √a² + b³ + 3 (a + √a² + b³ × a - √a² + b³)¹/3x
= 2a + 3(a² - a² - b³)¹/3x
= 2a + ( - 3bx)
∴ x³ + 3bx = 2a
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1 . 1 . 1 + 1 . 1 . 1 - 3 . 1 . 1 . 1 + 1 . 1 . 1 3 3 3 4 4 4 3 4 5 5 5 5 1 . 1 + 1 . 1 + 1 . 1 - 1 . 1 + 1 . 1 + 1 . 1 3 3 4 4 5 5 3 4 4 5 5 3
is equal to :
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Let 1 = a, 1 = b, and 1 = c 3 4 5
∴ Expression= a³ + b³ + c³ - 3abc a² + b² + c² - ab - ac - bc = (a + b + c) (a² + b² + c² - ab - ac - bc) = a + b + c a² + b² + c² - ab - ac - bc ⇒ 1 + 1 + 1 = 20 + 15 + 12 = 47 3 4 5 60 60 Correct Option: C
Let 1 = a, 1 = b, and 1 = c 3 4 5
∴ Expression= a³ + b³ + c³ - 3abc a² + b² + c² - ab - ac - bc = (a + b + c) (a² + b² + c² - ab - ac - bc) = a + b + c a² + b² + c² - ab - ac - bc ⇒ 1 + 1 + 1 = 20 + 15 + 12 = 47 3 4 5 60 60
- When xm is multiplied by xn, product is 1. The relation between m and n is
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xm × xm = 1
⇒ xm+n = x0
⇒ m + n = 0
⇒ m = –nCorrect Option: D
xm × xm = 1
⇒ xm+n = x0
⇒ m + n = 0
⇒ m = –n
- The term, that should be added to (4x² + 8x) so that resulting expression be a perfect square, is
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(a + b)² = a² + 2ab + b²
∴ 4x² + 8x + 4
= (2x)² + 2 × 2x × 2 + (2)²
= (2x + 2)²
∴ Required number = 4Correct Option: B
(a + b)² = a² + 2ab + b²
∴ 4x² + 8x + 4
= (2x)² + 2 × 2x × 2 + (2)²
= (2x + 2)²
∴ Required number = 4