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\(a,\left(6x+1\right)\left(x+2\right)-2x\left(3x-5\right)\)
\(=6x^2+12x+x+2-6x^2+10x\)
\(=23x+2\)
a) (6x + 1)(x + 2) - 2x(3x - 5)
= 6x2 + 12x + x + 2 - 6x2 + 10x
= (6x2 - 6x2) + (12x + x + 10x) + 2
= 23x + 2
b) (2x - 1)2 - (2x - 3)(2x + 3)
= 4x2 - 4x + 1 - 4x2 + 9
= (4x2 - 4x2) - 4x + (1 + 9)
= -4x + 10
c) (2x - 3)3 - (3x + 1)(5 - 4x) - 16x2
= 8x3 - 36x2 + 54x - 15x + 12x2 - 5 + 4x - 16x2
= 8x3 - (36x2 - 12x2 + 16x2) + (54x - 15x + 4x) - 5
= 8x3 - 40x2 + 43x - 5
d) (3x + 2) - (x - 5) - x(3x - 13)
= 3x + 2 - x + 5 - 3x2 + 13x
= (3x - x + 13x) + (2 + 5) - 3x2
= 15x + 7 - 3x2
\(A=2x^3+3\left(x-1\right)\left(x+1\right)-5x\left(x+1\right)\)
\(=2x^3+3\left(x^2-1\right)-5x^2-5x\)
\(=2x^3+3x^2-3-5x^2-5x\)
\(=2x^3-2x^2-5x-3\)
\(B=\left(5-2x\right)^3-\left(3x+5\right)\left(5-3x\right)\)
\(=125-150x+60x^2-8x^3-\left(25-9x^2\right)\)
\(=125-150x+60x^2-8x^3-25+9x^2\)
\(=100-15x+69x^2-8x^3\)
\(C=\left(3x+1\right)^2-\left(2x-1\right)^2\)
\(=\left(3x+1-2x+1\right)\left(3x+1+2x-1\right)\)
\(=\left(x+2\right).5x\)
\(D=\left(2x+1\right)^2+\left(3-x\right)^2-2\left(2x+1\right)\left(3-x\right)\)
\(=\left(2x+1-3+x\right)^2\)
\(=\left(3x-2\right)^2\)
\(E=\left(x-2\right)^3-x\left(x+1\right)\left(x-1\right)+6x\left(x-3\right)\)
\(=x^3-6x^2+12x-8+x\left(x^2-1\right)+6x^2-18x\)
\(=x^3-6x^2+12x-8+x^3-x+6x^2-18x\)
\(=-7x-8\)
\(F=\left(x-1\right)^3-3\left(1-x\right)\left(x+1\right)-\left(x^2+x+1\right)\left(x-1\right)-3x\)
\(=x^3-3x^2+3x-1-3\left(1-x^2\right)-\left(x^3-1\right)-3x\)
\(=x^3-3x^2+3x-1-3+3x^2-x^3+1-3x\)
\(=-3\)
a. gọi phần đầu đấy là A nhá, để đỡ cần viết lại
A=...............
= (3x+5)2 + ( 3x-5)2 - 9x2 -4
= (9x2 +30x + 25 ) + ( 9x2 -30x+ 25 ) - 9x2 -4
= 9x2 +30x + 25 + 9x2 -30x+25-9x2 -4
= 9x2 + 46
sai thì thôi nhé. bạn nên kiểm tra lại
d. (2x-1)*(4x2 + 2x +1 ) - 8x*( x2 +1) - 5
= 8x3 -1 - 8x3 -8x-5
= -8x-6
= -2(4x+3)
sai nhé. bạn nên kiểm tra lại
\(A=2x^3+3x^2-3-5x^2-5x=2x^3-2x^2-5x-3\\ B=125-150x+60x^2-8x^3-25+9x^2=-8x^3+69x^2-150x+100\\ C=\left(3x+1-2x+1\right)\left(3x+1+2x-1\right)=5x\left(x+2\right)=5x^2+10x\\ D=\left(2x+1-3+x\right)^2=\left(3x-2\right)^2=9x^2-12x+4\\ E=x^3-6x^2+12x-8-x^3+x+6x^2-18x=-5x-8\\ F=x^3-3x^2+3x-1-3+3x^2-x^3+1-3x=-3\)