要用方程
题目
要用方程
1 there is a double-digit number.The figure on its single is 1 larger than that on its tenth-digit ,and the double digit numbei is 5 times as large as the sum of figures on its tenth-digit and on its single-digit.Question:what is the double-digit number?2 there is a double-digit number.The figure on its tenth-digit is 1 smaller than that on its single digit.If the figures on its tenth-digit and on its single-digit are exchand,the newly-got number will be 9 larger than the original one.Question::what is the original double-digit?
答案
用一元.
两个数你设为x和x+1
(x+x+1)*5=10x+x+1
10x+5=11x+1
x=4
x+1=5
最后就是45了
举一反三
已知函数f(x)=x,g(x)=alnx,a∈R.若曲线y=f(x)与曲线y=g(x)相交,且在交点处有相同的切线,求a的值和该切线方程.
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