If x and y are positive integers and 1 + x + y + xy = 15, what is the value of x + y?
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(1+x)(1+y)=15
1 + x + y + xy看到这个形式应该就要转换成两个数相乘
1 + x + y + xy = 15 or (1+x)(1+y)=15 15 can be expressed as multiple (or the product?) of two integers as (1,15)and (3,5) if (1+x)(1+y)=1*15..1+x=1 or x=0 and y=14..so x+y=14.............not applicable if (1+x)(1+y)=3*5..1+x=3 or x=2 and y=4..so x+y=6....now edited
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(1+x)(1+y)=15
1 + x + y + xy看到这个形式应该就要转换成两个数相乘
1 + x + y + xy = 15
or (1+x)(1+y)=15
15 can be expressed as multiple (or the product?) of two integers as (1,15)and (3,5)
if (1+x)(1+y)=1*15..1+x=1 or x=0 and y=14..so x+y=14.............not applicable
if (1+x)(1+y)=3*5..1+x=3 or x=2 and y=4..so x+y=6....now edited