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If equations `x^2+a x+12=0. x^2+b x+15=0a n dx^2+(a+b)x+36=0,`have a common positive root, then find the values of `aa n dbdot` |
Answer» We have , `x^(2) + ax + 12 = 0` (1) `x^(2) + bx + 15 = 0` (2) `x^(2) + (a + b) x + 36 = 0` (3) Adding (1) and (2), we get `2x^(2)+ (a+ b) x + 27 = 0` Now subtracting it from the third equation, we get `x^(2) - 9 = 0 rArr x = 3, 3` Thus , the common positive root is 3, Hence, `9 + 12 + 3a = 0` `rArr a = - 7 and 9 + 3b + 15 = 0 ` `rArr b = -8` . |
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