x^2+3x-5=2

x^2+3x=7

Multiply both sides by 2 to get 2x 2+6x = 14, which is converted into 2x 2+6x-3 = 1 1.

The second question:

m^2-n^2=(m^2-mn)+(mn-n^2)=2 1+(- 12)=9

m^2-2mn+n^2=(m^2-mn)-(mn-n^2)=2 1-(- 12)=33

The third question:

Because when x=2, the value of AX 5+BX 3+CX+2 is -3, that is, AX 5+BX 3+CX =-5.

When x=-2, the value of AX 5+BX 3+CX is the reciprocal of x=2. I don't know if you can understand it, because the coefficient is constant, and x is odd power, and the odd power of-1 is-1, and you can see it by proposing-1.

So when x=-2, AX 5+BX 3+CX =+5, then AX 5+BX 3+CX+2 = 7.