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歡迎您訪問數學考題練習:若x2-y2=30,且x-y=-5,則x+y的!

數學考題練習:若x2-y2=30,且x-y=-5,則x+y的

更新時間:2024-01-12 16:41:34作者:貝語網校

若x2-y2=30,且x-y=-5,則x+y的值是

A.5

B.6

C.-6

D.-5

試題答案

C

試題解析

運用平方差公式先把x2-y2分解因式,再代入數據計算即可求出x+y的值.

解答:∵x2-y2=(x+y)(x-y)=30,x-y=-5,

∴x+y=-6.

故選C.

點評:本題考查了公式法分解因式,運用平方差公式先分解因式,再結合題意求出代數式的值,解決本題的關鍵是熟練掌握平方差公式.

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