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a , b എന്നിവ എണ്ണൽ സംഖ്യകളാണ്. a - b = 7, ab = 30 എങ്കിൽ a+b എത്ര ?

A15

B37

C210

D13

Answer:

D. 13

Read Explanation:

a - b = 7 ab = 30 (a-b)² = a² - 2ab + b² 7² = a² -2×ab + b² 7² + 4ab =a² -2ab + b² + 4ab 49 + 120 = a² +2ab + b² 169 = (a +b)² (a + b) = √169 = 13

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