Question

已知m-n=7,mn=2 求5n-3mn+5m+2

Answer 1

知m-n=7,mn=2 求5n-3mn+5m+2

(m+n ) ² =(m-n) ² +4mn

= 49 + 8

= 57

m+n = 正负 根号57

5n-3mn+5m+2

= 5n+5m -3mn +2

= 5 (m+n) - 3mn +2

= ±5 根号57 - 6 +2

= ±5 根号57 - 4

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