修改：在错的词下画一横线，并在该词下面写出修改后的词。

注意：1 每处错误及其修改均仅限一词；

2只允许修改10处，多者(从第11处起)不计分。

OnFriday, our teacher told us that there would an English corner in front of ourteaching building. I set about soon after the last class in the afternoon.

Tomy joy, the English corner had just been on for a few minute. I joined them ontheir talk. At first, I was afraid that my English was so poor and limit that Icouldn't follow them or make myself understand. I was also afraid that anyonemight laugh at me. But a smiling face here or an encouraging nod there soon putme at ease. Though I speak to them only in simple English that day, I believein future I will make a greater progress.

如果关于x的多项式 x⁴+（a-1）x³+5x²-（b+3）x-1不含x³项和x项，求a、b的值．

读北京图，回答下列问题．

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