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Find the nature of the roots of the equations of given below : (a) `x^(2) - 13x + 11 =0` (b ) `18x^(2) - 14x + 17 = 0` (c ) `9x^(2) - 36x + 36 = 0` (d) `3x^(2) - 5x - 8 = 0` |
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Answer» (a) Given `x^(2) - 13x + 11 = 0` Comparing it with `ax^(2) + bx + c = 0`, we have `a = 1, b = -13` and `c = 11`. Now, `b^(2) - 4ac = (-13)^(2) - 4(1)(11)` `= 169 - 44 = 125 lt 0`. `rArr b^(2) - 4ac gt 0` and is not perfet square. `:.` The roots are distinct and irrational . (b) Given `18x^(2) - 14x + 17 =0` Comparing it with `ax^(2) + bx + c = 0, a = 18, b = -14` and c = 17. Now , `b^(2) - 4ac = (-14)^(2) - 4(18) (17)` `= 196 - 1224` `= - 1028 lt 0` `rArr b^(2)-4ac lt 0`. `:.` The roots are imagniary. (c) Given `9x^(2) - 36x + 36 = 0`. `rArr 9(x^(2) - 4x+4) =0` `rArr x^(2) - 4x + 4 = 0` Comparing the above equation , with `ax^(2) + bx + c= 0, a= 1, b = - 4` and c = 4 Now, `b^(2)- 4ac = (-4)^(2) - 4(1)(4)` `= 16 - 16 = 0` `rArr b^(2) - 4ac = 0` `:.` The roots are equal. (d) Given `3x^(2) - 5x - 8 = 0` Comparing the above equation with `ax^(2) + bx + c = 0`, we getm `a = 3, b = -5` and `c = - 8`. Now, `b^(2)- 4ac = (-5)^(2) - 4(3) (-8)` `= 25+96 = 121 gt 0` , `rArr b^(2) - 4ac lt 0` and is a perfect square. `:.` The roots are rational and distinct. |
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