Algebra
- The maximum value of 5 + 20x – 4x2 , when x is a real number is :
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For y = ax2 + bx + c
Maximum value = c – b2 4a
Here, c = 5, b = 20, a = –4∴ Maximum value = 5 – 20 × 20 = 5 + 5 × 5 = 30 4 × −4 Correct Option: D
For y = ax2 + bx + c
Maximum value = c – b2 4a
Here, c = 5, b = 20, a = –4∴ Maximum value = 5 – 20 × 20 = 5 + 5 × 5 = 30 4 × −4
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If 1 (a − b) 2 + ab = p (a + b)2 ,then the value of p is : 2
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1 (a − b) 2 + ab = p (a + b)2 2 ⇒ 1 (a2 + b2 − 2ab) + ab = p (a + b)2 4 ⇒ 1 (a2 + b2 − 2ab + 4ab) = p (a + b)2 4 ⇒ 1 (a + b)2 = p (a + b)2 4 ⇒ p = 1 4 Correct Option: C
1 (a − b) 2 + ab = p (a + b)2 2 ⇒ 1 (a2 + b2 − 2ab) + ab = p (a + b)2 4 ⇒ 1 (a2 + b2 − 2ab + 4ab) = p (a + b)2 4 ⇒ 1 (a + b)2 = p (a + b)2 4 ⇒ p = 1 4
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If a + 1 2 = 3, then the value of a2 + 1 will be a a2
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a + 1 2 = 3 a ⇒ a2 + 1 + 2 = 3 a2 ⇒ a2 + 1 = 3 − 2 = 1 a2 Correct Option: B
a + 1 2 = 3 a ⇒ a2 + 1 + 2 = 3 a2 ⇒ a2 + 1 = 3 − 2 = 1 a2
- If (a + b – 6)2 + a2 + b2 + 1 + 2b = 2ab + 2a, then the value of a is
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(a + b – 6)2 + a2 + b2 + 1 + 2b = 2ab + 2a
⇒ (a + b – 6)2 + a2 + b2 +1 + 2b – 2ab – 2a = 0
⇒ (a + b – 6)2 + (a)2 + (–b)2 + (–1)2 + 2a (–b) + 2 (–b) (–1) + 2 (a) (–1) = 0
⇒ (a + b – 6)2 + (a – b – 1)2 = 0
⇒ a + b – 6 = 0 and a – b – 1 = 0
⇒ a + b = 6 and a – b = 1
On adding these two equations,
a + b + a – b = 6 + 1
⇒ 2a = 7⇒ a = 7 = 3.5 2 Correct Option: C
(a + b – 6)2 + a2 + b2 + 1 + 2b = 2ab + 2a
⇒ (a + b – 6)2 + a2 + b2 +1 + 2b – 2ab – 2a = 0
⇒ (a + b – 6)2 + (a)2 + (–b)2 + (–1)2 + 2a (–b) + 2 (–b) (–1) + 2 (a) (–1) = 0
⇒ (a + b – 6)2 + (a – b – 1)2 = 0
⇒ a + b – 6 = 0 and a – b – 1 = 0
⇒ a + b = 6 and a – b = 1
On adding these two equations,
a + b + a – b = 6 + 1
⇒ 2a = 7⇒ a = 7 = 3.5 2
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If x + 3y = – 3x + y, then x2 is equal to 2y2
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x + 3y = – 3x + y
⇒ x + 3x = – 3y + y
⇒ 4x = – 2y
⇒ 2x = – y⇒ x = − 1 y 2 ∴ x2 = − 1 2 y2 2 = 1 4 ∴ x2 = 1 × 1 = 1 2y2 2 4 8 Correct Option: A
x + 3y = – 3x + y
⇒ x + 3x = – 3y + y
⇒ 4x = – 2y
⇒ 2x = – y⇒ x = − 1 y 2 ∴ x2 = − 1 2 y2 2 = 1 4 ∴ x2 = 1 × 1 = 1 2y2 2 4 8