已知:A+B=3x²-5x-1,A-C=-2x+3x²-5,且丨x丨=二分之一,求B+C的值
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![已知:A+B=3x²-5x-1,A-C=-2x+3x²-5,且丨x丨=二分之一,求B+C的值](/uploads/image/z/12878193-57-3.jpg?t=%E5%B7%B2%E7%9F%A5%3AA%2BB%3D3x%26%23178%3B-5x-1%2CA-C%3D-2x%2B3x%26%23178%3B-5%2C%E4%B8%94%E4%B8%A8x%E4%B8%A8%3D%E4%BA%8C%E5%88%86%E4%B9%8B%E4%B8%80%2C%E6%B1%82B%2BC%E7%9A%84%E5%80%BC)
已知:A+B=3x²-5x-1,A-C=-2x+3x²-5,且丨x丨=二分之一,求B+C的值
已知:A+B=3x²-5x-1,A-C=-2x+3x²-5,且丨x丨=二分之一,求B+C的值
已知:A+B=3x²-5x-1,A-C=-2x+3x²-5,且丨x丨=二分之一,求B+C的值
B+C
=(A+B)-(A-C)
=(3x²-5x-1)-(-2x+3x²-5)
= -3x+4
∵丨x丨=1/2 ,∴x=1/2或者x=-1/2
当x=1/2时,B+C= -3x+4=-3*(1/2)+4=5/2;
当x=-1/2时,B+C= -3x+4=-3*(-1/2)+4=11/2;