c,4x²-20x+25-4x²-20x-25+40x-1

=-1

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

\(=5\left(4x^2-4x+1\right)+\left(4x-4\right)\cdot\left(x+3\right)+2\left(25-30x+9x^2\right)\)

\(=20x^2-20x+5+4x^2+12x-4x-12+50-60+18x^2\)

\(=42x^2-72x+43\)

2) \(C=\left(2a^2+2a+1\right)\left(2a^2-2a+1\right)-\left(2a+1\right)^2\)

\(=4a^4-4a^3+2a^2+4a^3-4a^2+2a+2a^2-2a+1-\left(4a^2+4a+1\right)\)

\(=4a^4+2a^2-4a^2+2a^2+1-4a^2-4a-1\)

\(=4a^4-4a^2-4a\)

3) Sky Sơn Tùng làm đúng rồi nhé.

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

\(=x^4+27x^2+1-10x^3+250x^5-1400x^4+1030x^3-302x^2+40x-2\)

\(=-1399x^4-275x^2-1+1020x^3+250x^5+40x\)

5) \(F=\left(a^2+b^2-c^2\right)^2-\left(a^2-b^2+c^2\right)^2\)

\(=\left[a^2+b^2-c^2-\left(a^2-b^2+c^2\right)\right]\cdot\left(a^2+b^2-c^2+a^2-b^2+c^2\right)\)

\(=\left(a^2+b^2-c^2-a^2+b^2-c^2\right)\cdot2a^2\)

\(=\left(2b^2-2c^2\right)\cdot2a^2\)

\(=2\left(b^2-c^2\right)\cdot2a^2\)

\(=2\left(b-c\right)\left(b+c\right)\cdot2a^2\)

\(=2\cdot2a^2\cdot\left(b-c\right)\left(b+c\right)\)

\(=4a^2\cdot\left(b-c\right)\left(b+c\right)\)

6) \(G=\left(a+b+c\right)^2+\left(a+b-c\right)^2-2\left(a+b\right)^2\)

\(=a^2+b^2+c^2+2ab+2ac+2bc+a^2+b^2+\left(-c\right)^2+2ab-2ac-2bc-2\left(a^2+2ab+b^2\right)\)

\(=a^2+b^2+c^2+2ab+a^2+b^2+\left(-c\right)^2+2ab-2a^2-4ab-2b^2\)

\(=0+0+c^2+0+c^2\)

\(=2c^2\)

7) \(H=\left(a+c\right)\left(a-c\right)-\left(a-b-c\right)\left(a-b+c\right)+b\left(b-2x\right)\)

\(=a^2-c^2-\left[\left(a-b\right)^2-c^2\right]+b^2-2bx\)

\(=a^2-c^2-\left(a^2-2ab+b^2-c^2\right)+b^2-2bx\)

\(=a^2-b^2-a^2+2ab-b^2+c^2+b^2-2bx\)

\(=2ab-2bx\)

\(D=\left(9x-1\right)^2+\left(1-5x\right)^2+2\left(9x-1\right)\left(1-5x\right)=\left(9x-1+1-5x\right)^2=\left(4x\right)^2=16x^2\)

sao chữ càng ngày càng nhỏ zợ , mk cận  T_T

a) 5.(2x-1)²+4.(x-1).(x+3-2).(5-3x)²

=20x²-20x+5+36x⁴-120x³+64x²+120x-100

=36x⁴+(-20x+120x)+(5-100)+(64x²+20x²)-120x³

=36x⁴+100x-95+84x²-120x³

b,c,d bn tự tính nhé bậc cao qá nên khó tính

A= (6x-2)^2 + (2-5x)^2+2(6x-2)(2-5x)

= (6x-2)^2 +2(6x-2)(2-5x)+ (2-5x)^2

\(=\left(6x-2+2-5x\right)^2=x^2\)

B= (2a^2+2a+1)(2a^2-2a+1)-(2a^2+1)^2

\(=\left(2a^2+1\right)^2-4a^2-\left(2a^2+1\right)^2=4a^2\)

C=(x+3)(x^2-3x+9)-(54+x^3)

\(=\left(x^3+27\right)-54-x^3=27\)

D=(2x+y)(4x^2-2xy+y^2)-(2x-y)(4x^2+2xy+y^2)

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

E=(a+b)^2-(a-b)^2

\(=\left(a+b+a-b\right)\left(a+b-a+b\right)=2a.2b=4ab\)

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\(C=\left(x+3\right)\left(x^2-3x+9\right)-\left(54+x^3\right)\)

\(=x^3-27-54-x^3=-81\)

\(C=\left(x+3\right)\left(x^2-3x+9\right)-\left(54+x^3\right)\)

\(=x^3+27-54-x^3=-27\)