已知:a+b=3X²-5X+4,a-c=3X²+2X-5.求:当X=4,b+c的值
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![已知:a+b=3X²-5X+4,a-c=3X²+2X-5.求:当X=4,b+c的值](/uploads/image/z/120666-66-6.jpg?t=%E5%B7%B2%E7%9F%A5%3Aa%2Bb%3D3X%26%23178%3B-5X%2B4%2Ca-c%3D3X%26%23178%3B%2B2X-5.%E6%B1%82%3A%E5%BD%93X%3D4%2Cb%2Bc%E7%9A%84%E5%80%BC)
已知:a+b=3X²-5X+4,a-c=3X²+2X-5.求:当X=4,b+c的值
已知:a+b=3X²-5X+4,a-c=3X²+2X-5.求:当X=4,b+c的值
已知:a+b=3X²-5X+4,a-c=3X²+2X-5.求:当X=4,b+c的值
b+c=(a+b)-(a-c)
=3x²-5x+4-3x²-2x+5
=-7x+9
当x=4时
b+c=-28+9
=-19
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