(x-2)(x-3)-3(x^2-7x+13)其中x=7/2
问题描述：
(x-2)(x-3)-3(x^2-7x+13)其中x=7/2
答
因为x=7/2
所以x^2=7x/2
2x^2=7x
(x-2)(x-3)-3(x^2-7x+13)
=x^2-5x+6-3(x^2-7x+13)
=-2x^2+16x-33
=-7x+16x-33
=9x-33
=9*7/2-33
=-3/2
答
原式=x^2-5x+6-3x^2+21x-39
=-2x^2+16x-33
带入x=7/2，可得原式=-2*49/4+16*7/2-33
=112/2-49/2-66/2
=-3/2
答
原式
=x²-5x+6-3(x²-7x+13)
=x²-5x+6-3x²+21x-39
=-2x²+16x-33
=-2*49/4+16*7/2-33
=-49/2+56-33
=-3/2