Question

(3x+1)²+2(x+1)(x-1)-3(2x-5)²

Answer 1

9x²+6x+1+2(x²-1)-3(4x²-20x+25)=
9x²+6x+1+2x²-2x-12x²+60x-75=
-x²+64x-74

Answer 2

(3x+1)² [scrii formula] $(3x)^{2} +2*3x*1+ 1^{2} =9 x^{2} +6x+1 \\ (x+1)(x-1)= [scrii formula]x^{2} - 1^{2} = x^{2} -1 \\ (2x-5)^{2} =[scrii formula] (2x)^{2} -2*2x*5+ 5^{2} =4 x^{2} -20x+25 \\ [inlocuim. ce. avem]=> 9 x^{2} +6x+1 + 2 (x^{2} -1 )-3(4 x^{2} -20x+25 )=\\ = 9 x^{2} +6x+1 + 2 x^{2} -2x-12 x^{2} +60x-75= \\ =- x^{2} +64x-74$