Question

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15-(a+3)(a-3)=
(a+b)(a-b)-(a-b)^2=
(2a+1)^2+(1-2a)(1+2a)=

2х-(5-3х-4)=х-5

Answer 1

15-(a+3)(a-3)=15-a²+9=-a²+24
(a+b)(a-b)-(a-b)^2=a²-b²-a²+2ab-b²=-2b²+2ab
(2a+1)^2+(1-2a)(1+2a)=4a²+4a+1+1-4a²=4a+2

2х-(5-3х-4)=х-5
2x-5+3x+4=x-5
5x-x=-5-4+5
4x=-4|:4
x=-1