\(\left(3x+1\right)^2-2\left(3x+1\right)\left(3x+5\right)+\left(3x+5\right)^2\)

\(=\left[\left(3x+1\right)-\left(3x+5\right)\right]^2\)

\(=\left(3x+1-3x-5\right)^2\)

\(=\left(-4\right)^2=16\)

\(a,\left(3x+1\right)^2-2\left(3x+1\right)\left(3x-5\right)+\left(3x-5\right)^2=\left(\left(3x+1\right)-\left(3x-5\right)\right)^2=6^2=36\)
\(b,\left(3x^2-y\right)^2-\left(2x^2+y\right)^2=\left(3x^2-y-2x^2-y\right)\left(3x^2-y+2x^2+y\right)=\left(x^2-2y\right).5x^2\)

a. BT= ((3x+1) - (3x-5))²=6²=36

b. BT = (3x²-y-2x²-y). (3x²- y + 2x²+ y) = (x²-2y).5x²

a) \(\left(3x+1\right)^2-2\left(3x+1\right)\left(3x-5\right)+\left(3x-5\right)^2\)

\(=\left[\left(3x+1\right)^2-\left(3x+1\right)\left(3x-5\right)\right]-\left[\left(3x+1\right)\left(3x-5\right)-\left(3x-5\right)^2\right]\)

\(=\left[\left(3x+1\right)\left(3x+1-3x+5\right)\right]-\left[\left(3x+1-3x+5\right)\left(3x-5\right)\right]\)

\(=\left[6\left(3x+1\right)\right]-\left[6\left(3x-5\right)\right]\)

\(=6\left(3x+1-3x+5\right)\)

\(=6.6=36\)

câu a là hằng đẳng thức luôn

A=(2x+4)^2

B khai triển tung tóe ra thì phần sau triệt tiêu hết còn 4(a^2+b^2+c^2)

câu c cảm giác sai đề vì mấy câu này phải là (3x)^ ms ra hdt chứ nhỉ

\(a,\left(3x+5\right)^2+\left(3x-5\right)^2-\left(3x+2\right)\left(3x-2\right)=9x^2+30x+25+9x^2-30x+25-9x^2+4=9x^2+54\)
\(b,BT=2x\left(4x^2-4x+1\right)-3x\left(x^2-9\right)-4x\left(x^2+2x+1\right)=8x^3-8x^2+2x-3x^3+27x-4x^3-8x^2-4x=x^3-16x^2+25x\)
\(c,BT=\left(x+y-z\right)^2-2\left(x+y-z\right)\left(x+y\right)+\left(x+y\right)^2=\left(x+y-z-x-y\right)^2=z^2\)

\(\left(3x-5\right)^2+\left(x+2\right)^2+x\left(3-4x\right)\)

\(=9x^2-30x+25+x^2+4x+4+3x-4x^2\)

\(=6x^2-23x+29\)

\(=25-30x+9x^2+x^2+4x+4+3x-12x^2=-2x^2-23x+29\)

\(\left(3x-4\right)^2-2\left(3x-4\right)\left(x-4\right)+\left(x-4\right)^2\)

\(=\left(3x-4-x+4\right)^2\)

\(=4x^2\)

\(\left(3x-4\right)^2+\left(4-x\right)^2-2\left(3x-4\right)\left(x-4\right)=\left(3x-4\right)^2-2\left(3x-4\right)\left(x-4\right)+\left(x-4\right)^2=\left(3x-4-x+4\right)^2=\left(2x\right)^2=4x^2\)

\(\left(5-3x\right)\left(5+3x\right)-\left(x+1\right)^3\)

\(=25-9x^2-x^3-3x^2-3x-1\)

\(=-x^3-12x^2-3x+24\)

\(\left(3x+1\right)^2-2\left(3x+1\right)\left(3x+5\right)+\left(3x+5\right)^2=\left(3x+1-3x-5\right)^2=\left(-4\right)^2=16\)

Dùng hằng đẳng thức số hai nha bạn....

\(\left(3x+1\right)^2-2\left(3x+1\right)\left(3x+5\right)+\left(3x+5\right)^2\)

\(=\left(3x+1-3x-5\right)^2\)

\(=\left(-4\right)^2=16\)

dấu đằng trước là bạn viết nhầm hay là dấu trừ vậy?

nhầm á