1, \(3x^2-2x\left(5+1,5x\right)+10\)

= \(3x^2-10x-3x^2+10\)

= \(10-10x\)

= \(10\left(1-x\right)\)

\(\text{a)}3x^2-2x\left(5+1.5x\right)+10\\ =3x^2-10x+3x^2+10\\ =\left(3x^2+3x^2\right)-10x+10\\ =6x^2-10x+10\)

\(\text{b)}5x\left(3x^2-12x+6\right)+4x^3\\ =15x^3-60x^2+30x+4x^3\\ =\left(15x^3+4x^3\right)-60x^2+30x\\ =19x^3-60x^2+30x\)

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a) \(3x^2-2x\left(5+1,5x\right)+10x\)

\(=3x^2-10x-3x^2+10x=0\)

b) \(7x\left(4y-x\right)+4y\left(y-7x\right)-2\left(2y^2-3,5x\right)\)

\(=28xy-7x^2+4y^2-28xy-4y^2+7x\)

\(=-7x^2+7x\)

a. \(3x^2-2x\left(5+1.5x\right)+10\)

\(=3x^2-10x-3x^2+10\)

\(=-10x+10\)

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

\(=x^3-2x^2+3x-4x^2+8x-12\)

\(=x^3-6x^2+11x-12\)

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

\(=10x^3-15x^2-5x+4x^2-6x-2\)

\(=10x^3-11x^2-11x-2\)

d. \(\left(25x^2+10xy+4y^2\right)\left(5x+2y\right)\)

\(=125x^3+50x^2y+20xy^2+50x^2y+10xy^2+6y^3\)

\(=125x^3+100x^2y+30xy^2+6y^3\)

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

\(=20x^5-4x^4+2x-12x^2-5x^4+x^3-2x^2+3x+10x^3-2x^2+4x-1\)

\(=20x^5-9x^4+9x-16x^2+11x^3+1\)

\(3x^2-2x\left(5+1,5x\right)+10\)

\(=3x^2-10x-3x^2+10\)

\(=-10x+10\)

\(B=\left(3x-1\right)^2-\left(x+7\right)^2-2\left(2x-5\right)\left(2x+5\right)\)

\(=9x^2-6x+1-\left(x^2+14x+49\right)-2\left(4x^2-25\right)\)

\(=9x^2-6x+1-x^2-14x-49-8x^2+50\)

\(=-20x+2\)

Thay x=1/5 vào B, ta được:

\(B=-20\cdot\dfrac{1}{5}+2=-4+2=-2\)