(1).(2m+3)(2m-3)(2).x(x+1)+(2-x)(2+x)(3).(3x-y)(3x+y)+y(x+y)(4).(a+1/2b)(a-1/2b)-(3a-2b)(3a+2b)用平方差公式计算:(1).1007*993(2).108*112

Question

(1).(2m+3)(2m-3)
(2).x(x+1)+(2-x)(2+x)
(3).(3x-y)(3x+y)+y(x+y)
(4).(a+1/2b)(a-1/2b)-(3a-2b)(3a+2b)
用平方差公式计算:
(1).1007*993
(2).108*112

Answer 1

(1).(2m+3)(2m-3)
用平方差
=4m^2-9
(2).x(x+1)+(2-x)(2+x)
=x^2+x+4-x^2
=x+4
(3).(3x-y)(3x+y)+y(x+y)
=9x^2-y^2+xy+y^2
=9x^2+xy
(4).(a+1/2b)(a-1/2b)-(3a-2b)(3a+2b)
=a^2-1/4b^2-(9a^2-4b^2)
=a^2-1/4b^2-9a^2+4b^2
=-8a^2+15/4b^2
用平方差公式计算:
(1).1007*993
=(1000+7)*(1000-7)
=1000^2-7^2
=1000000-49
=999951
(2).108*112
=(110-2)*(110+2)
=110^2-2^2
=12100-4
=12096