If the length of a rectangle is reduced by 1 cm and the width is increased by 3 cm, the square will be 21 cm larger than the original rectangle. What is the length and width of the original rectangle? As soon as possible

If the length of a rectangle is reduced by 1 cm and the width is increased by 3 cm, the square will be 21 cm larger than the original rectangle. What is the length and width of the original rectangle? As soon as possible

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Let the length of the original rectangle be x and the width be y
According to the meaning of the title:
x-1=y+3 ①
(x-1)(y+3)-21=xy ②
The results are as follows:
x=y+4 ③
Substituting (3) into (2), the algebraic formula is obtained
6y-13=4y
y=6.5
Substituting y = 6
x=6.5+4=10.5
So the length is 10.5 and the width is 6.5
A: the original rectangle is 10.5cm long and 6.5cm wide