Phân tích đa thức thành nhân tử :
\(-5^my+15x^ny\)
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7x2+15x-5=0
7*(x2+2.5x-5/7)=0
x2+2*x*1.25+1,5625-255/112=0
(x+1.25)2-255/112=0
\(1,\\ 1,=15\left(x+y\right)\\ 2,=4\left(2x-3y\right)\\ 3,=x\left(y-1\right)\\ 4,=2x\left(2x-3\right)\\ 2,\\ 1,=\left(x+y\right)\left(2-5a\right)\\ 2,=\left(x-5\right)\left(a^2-3\right)\\ 3,=\left(a-b\right)\left(4x+6xy\right)=2x\left(2+3y\right)\left(a-b\right)\\ 4,=\left(x-1\right)\left(3x+5\right)\\ 3,\\ A=13\left(87+12+1\right)=13\cdot100=1300\\ B=\left(x-3\right)\left(2x+y\right)=\left(13-3\right)\left(26+4\right)=10\cdot30=300\\ 4,\\ 1,\Rightarrow\left(x-5\right)\left(x-2\right)=0\Rightarrow\left[{}\begin{matrix}x=2\\x=5\end{matrix}\right.\\ 2,\Rightarrow\left(x-7\right)\left(x+2\right)=0\Rightarrow\left[{}\begin{matrix}x=7\\x=-2\end{matrix}\right.\\ 3,\Rightarrow\left(3x-1\right)\left(x-4\right)=0\Rightarrow\left[{}\begin{matrix}x=\dfrac{1}{3}\\x=4\end{matrix}\right.\\ 4,\Rightarrow\left(2x+3\right)\left(2x-1\right)=0\\ \Rightarrow\left[{}\begin{matrix}x=-\dfrac{3}{2}\\x=\dfrac{1}{2}\end{matrix}\right.\)
\(12x+15x^2y=3x.4+3x.5xy=3x\left(4+5xy\right)\)
\(\text{Vậy } 12x + 15x^2y=3x(4+5xy)\)
6x^2 + 15x - 36
= 6x^2 + 24x - 9x - 36
= (6x^2 + 24x) - (9x + 36)
= 6x(x + 4) - 9(x+4)
= (6x - 9) (X + 4)
= 3(2x - 3)(x + 4)
\(6x^2+15-36\)
\(=3\left(2x^2+5x-12\right)\)
\(=3\left(2x^2+8x-3x-12\right)\)
\(=3\left[2x\left(x+4\right)-3\left(x+4\right)\right]\)
\(=3\left(2x-3\right)\left(x+4\right)\)
5x2 (x – 2y)– 15x(x – 2y) = x.5x(x - 2y) - 3.5x(x - 2y)
= (x - 3).5x(x - 2y)
\(=\left(x^2+x+4\right)^2+3x\left(x^2+x+4\right)+5x\left(x^2+x+4\right)+15x^2\\ =\left(x^2+x+4\right)\left(x^2+x+4+3x\right)+5x\left(x^2+x+4+3x\right)\\ =\left(x^2+x+4+3x\right)\left(x^2+x+4+5x\right)\\ =\left(x^2+4x+4\right)\left(x^2+6x+4\right)\\ =\left(x+2\right)^2\left(x^2+6x+4\right)\)
\(-5^my+15x^ny\)
\(=5y\left(3x^n-5^{m-1}\right)\)
Tham khảo~
Xét 2 trường hợp :
Trường hợp 1 :
\(m\ge n\)
\(\Rightarrow-5^my+15x^my\)
\(=-5x^n.x^{m-n}y+15x^ny\)
\(=-5x^ny\left(x^{m-n}-3\right)\)
Trường hợp 2 :
\(m< n\)
\(\Rightarrow-5^my+15x^ny\)
\(=-5x^my+15x^m.x^{n-m}y\)
\(=-5x^my\left(1-3x^{n-m}\right)\)