(15-X)(15-X)=25X X等于多少呢?
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(15-X)(15-X)=25X X等于多少呢?
![(15-X)(15-X)=25X X等于多少呢?](/uploads/image/z/1578793-49-3.jpg?t=%2815-X%29%2815-X%29%3D25X+X%E7%AD%89%E4%BA%8E%E5%A4%9A%E5%B0%91%E5%91%A2%3F)
(15-x)(15-x)=25x
225-30x+x²=25x
x²-55x+225=0
x=(-b±√b²-4ac)/2a
=(55±√55²-4×1×225)/2
=55±√3025-900)/2
=(55±√2125)/2
解得:x1=(55+5√85)/2 x2=(55-5√85)/2
225-30x+x²=25x
x²-55x+225=0
x=(-b±√b²-4ac)/2a
=(55±√55²-4×1×225)/2
=55±√3025-900)/2
=(55±√2125)/2
解得:x1=(55+5√85)/2 x2=(55-5√85)/2