作业帮数学计算题,前两题要用简便方法哦,1、(2x-3y-1)(2x+3y+1) 2、(a+b-c)(a-b+c)3、(2x-1)(2x+1)-2(x-2)(x+2)4、(t-2)^2 (t^2+4)^2 (t+2)^2
来源：学生作业帮助网 编辑：作业帮 时间：2024/05/14 19:19:02
数学计算题,前两题要用简便方法哦,
1、(2x-3y-1)(2x+3y+1)
2、(a+b-c)(a-b+c)
3、(2x-1)(2x+1)-2(x-2)(x+2)
4、(t-2)^2 (t^2+4)^2 (t+2)^2
1、
(2x-3y-1)(2x+3y+1)
=[2x-(3y+1)][2x+(3y+1)]
=(2x)^2-(3y+1)^2
=4x^2-(9y^2+1+6y)
=4x^2-9y^2-6y-1
2、
(a+b-c)(a-b+c)
=[a+(b-c)][a-(b-c)]
=a^2-(b-c)^2
=a^2-(b^2+c^2+2bc)
=a^2-b^2-c^2-2bc
3、
(2x-1)(2x+1)-2(x-2)(x+2)
=(2x)^2-1-2(x^2-4)
=4x^2-1-2x^2+8
=2x^2+7
4、
(t-2)^2 (t^2+4)^2 (t+2)^2
=(t-2)^2 (t+2)^2(t^2+4)^2
=[(t-2)(t+2)]^2(t^2+4)^2
=(t^2-4)^2(t^2+4)^2
=[(t^2-4)(t^2+4)]^2
=(t^4-16)^2
=t^8+256-32t^4