映射的公式,映射个数公式怎么推

[ 0，1 ] xxminxmaxminfrac { x-xmin } { xmax-xmin }映射到xmaxxminxxmin

[a，b ]映射到b]xxmInxmaxmIn(ba ) a(FRAC(x-xmin ) xmax-xmin ) *(B-a ) axmaxxminxxmin (ba ) a )