X(x-1)➗2=15 X*(x-1)/2=15
x(x-1)/2=15\u600e\u4e48\u89e3?\u8981\u6700\u8be6\u7ec6\u7684\u89e3\u6cd5\uff0c\u4e00\u6b65\u4e00\u6b65\u89e3x(x-1)/2=15
x(x-1)=30
x²-x-30=0
(x+5)(x-6)=0
x+5=0\u6216x-6=0
x1=-5
x2=6
x²-x=30
x²-x-30=0
(x-6)(x+5)=0
x=6,x=-5
方法如下,
请作参考:
x1=6,x2=-5
解:x(x―1)÷2=15
x²―x=30
(x―1/2)²=30+1/4=121/4
x―1/2=±11/2
x1=11/2+1/2=6
x2=―11/2+1/2=―5
两边同时乘以2
x(x-1)=30
去括号,移项,变形为
x^2-x-30=0
因式分解
(x-6)(x+5)=0
所以解得
x=6或x=-5
解:x(x-1)÷2=15
x(x-1)=30
xx-x-30=0
(x+5)(x-6)=0
x+5=0
x1=-5
x-6=0
x2=6
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