Quadratic Equation
Direction: In the following questions two equations numbered I and II are given. You have to solve both the equations and give answer
( 1 ) if x > y
( 2 ) if x ≥ y
( 3 ) if x < y
( 4 ) if x ≤ y
( 5 ) if x = y or the relationship cannot be established.
- Ⅰ. 2x2 + 11x + 14 = 0
Ⅱ. 4y2 + 12y + 9 = 0
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From the given equations , we have
Ⅰ. 2x2 + 11x + 14 = 0
⇒ 2x2 + 7x + 4x + 14 = 0
⇒ x( 2x + 7 ) + 2( 2x + 7 ) = 0
Ⅱ. 4y2 + 12y + 9 = 0
⇒ ( 2y + 3 )2 = 0Correct Option: C
From the given equations , we have
Ⅰ. 2x2 + 11x + 14 = 0
⇒ 2x2 + 7x + 4x + 14 = 0
⇒ x( 2x + 7 ) + 2( 2x + 7 ) = 0
⇒ ( x + 2 )( 2x + 7 ) = 0⇒ x = -7 or -2 2
Ⅱ. 4y2 + 12y + 9 = 0
⇒ ( 2y + 3 )2 = 0
⇒ ( 2y + 3 )( 2y + 3 ) = 0
From above both equations it is clear that x < y is correct answer .⇒ y = -3 , -3 2 2
- The roots of the equation ax2 + bx + c = 0 will be reciprocal if
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As we know that ,
For reciprocal roots, product of roots must be 1∴ c = I ⇒ c = a a Correct Option: C
As we know that ,
For reciprocal roots, product of roots must be 1∴ c = I ⇒ c = a a
Thus , required answer is c = a .
- Find the value of √30 + √30 + √30 +........
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According to question ,we can say that
Let , x = √30 + √30 + √30 +........
On squaring both sides, we have
x2 = 30 + √30 + √30 + √30 +........
⇒ x2 = 30 + x ⇔ x2 - x - 30 = 0
⇒ x2 - 6x + 5x - 30 = 0Correct Option: C
According to question ,we can say that
Let , x = √30 + √30 + √30 +........
On squaring both sides, we have
x2 = 30 + √30 + √30 + √30 +........
⇒ x2 = 30 + x ⇔ x2 - x - 30 = 0
⇒ x2 - 6x + 5x - 30 = 0
⇒ x( x - 6 ) + 5( x - 6 ) = 0
⇒ ( x - 6 ) ( x + 5 ) = 0
⇒ x = 6 because x ≠ - 5
Hence , required answer is 6 .
- The sum of the squares of 2 natural consecutive odd numbers is 394. The sum of the numbers is :
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Let, the two natural consecutive odd numbers be n and (n + 2)
Now, according to the question,
⇒ n2 + ( n + 2 )2 = 394
⇒ n2 + n2 + 4 + 4n = 394Correct Option: D
Let, the two natural consecutive odd numbers be n and (n + 2)
Now, according to the question,
⇒ n2 + ( n + 2 )2 = 394
⇒ n2 + n2 + 4 + 4n = 394
⇒ 2n2 + 4n - 390= 0
⇒ n2 + 2n - 195 = 0
⇒ n2 + 15n - 13n - 195 = 0
⇒ n( n + 15 ) - 13( n + 15 ) = 0
⇒ ( n + 15 ) ( n - 13 ) = 0
⇒ n = 13 and n ≠ - 15
∴ The two natural consecutive odd numbers be 13 and (13 + 2) = 15 .
∴ the sum of the numbers = 13 + 15 = 28
Quicker Approach:
By mental operation, 132 + 152 = 169 + 225 = 394
∴ Required sum = 13 + 15 = 28
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One root of the equation 3x2 - 10x + 3 = 0 is 1 . Find the other root. 3
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The given quadratic equation is 3x2 - 10x + 3 = 0
Comparing with ax2 + bx + c = 0, we get
a = 3, b = −10, c = 3Correct Option: A
The given quadratic equation is 3x2 - 10x + 3 = 0
Comparing with ax2 + bx + c = 0, we get
a = 3, b = −10, c = 3∴ Sum of the roots ( k1 + k2 ) = - a = 10 b 3 ∵ One root k1 = 1 3 ∴ The other root k2 = 10 - 1 = 9 = 3. 3 3 3
Therefore , The other root is 3 .