maths問題

1.(1-2x)(1+2x)
= 1+2x-2x-4x^2
= 1- 4x^2

2.(2y-3x)(2y+3x)
= 4y^2+6xy-6xy-9x^2
= 4y^2- 9x^2

3.(7u-3v)(7u+3v)
= 49u^2+21uv-21uv-9v^2
= 49u^2- 9v^2

1.
1-4x^2=0
x^2=1/4
x=1/2
2.
4y^2=9x^2
y=3x^2 let y=1 then x=2/3
3.
49u^2-9v^2=0
7u=9v let u=1 then v=7/9

1.(1-2x)(1+2x)=1^2-(2x)^2=1-4x^2
2.(2y-3x)(2y+3x)= (2y)^2-(3x)^2=4y^2-9x^2
3.(7u-3v)(7u+3v)= (7u)^2-(3v)^2=49u^2-9v^2
[^2]-->2次方

1.2x
2.4y
3.14u