Toán Lớp 8: x^ 2 -5x+6;
3x ^ 2 – 5x – 2
-) x^ 4 +2x^ 3 +6x-9;
Thân tích đa thức thành nhân tử:
x^ 2 -3x+2;
2x^ 2 +5x+2:
x^ 4 -2x^ 3 +x^ 2 -9,
b) 3x ^ 2 + 9x – 30
d) x^ 3 -7x-6;
f) x ^ 2 – 7xy + 10y ^ 2 .
b) 4x^ 2 -36x+56;
d) x^ 3 +2x-x^ 2 -2;
f) x ^ 2 – 3xy + 2y ^ 2 .
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{x^2} – 5x + 6\\
= {x^2} – 2x – 3x + 6\\
= \left( {x – 2} \right)\left( {x – 3} \right)\\
3{x^2} – 5x – 2\\
= 3{x^2} – 6x + x – 2\\
= \left( {x – 2} \right)\left( {3x + 1} \right)\\
{x^4} + 2{x^3} + 6x – 9\\
= {x^4} – 9 + 2x\left( {{x^2} + 3} \right)\\
= \left( {{x^2} + 3} \right)\left( {{x^2} – 3} \right) + 2x\left( {{x^2} + 3} \right)\\
= \left( {{x^2} + 3} \right)\left( {{x^2} – 3 + 2x} \right)\\
{x^2} – 3x + 2 = \left( {x – 1} \right)\left( {x – 2} \right)\\
2{x^2} + 5x + 2 = \left( {2x + 1} \right)\left( {x + 2} \right)\\
{x^4} – 2{x^3} + {x^2} – 9??\\
b)3{x^2} + 9x – 30\\
= 3\left( {{x^2} + 3x – 10} \right)\\
= 3.\left( {{x^2} + 5x – 2x – 10} \right)\\
= 3\left( {x + 5} \right)\left( {x – 2} \right)\\
d){x^3} – 7x – 6\\
= {x^3} + {x^2} – {x^2} – x – 6x – 6\\
= \left( {x + 1} \right)\left( {{x^2} – x – 6} \right)\\
= \left( {x + 1} \right)\left( {x – 3} \right)\left( {x + 2} \right)\\
f){x^2} – 7xy + 10{y^2}\\
= {x^2} – 2xy – 5xy + 10{y^2}\\
= \left( {x – 2y} \right)\left( {x – 5y} \right)\\
b)4{x^2} – 36x + 56\\
= 4.\left( {{x^2} – 9x + 14} \right)\\
= 4\left( {x – 2} \right)\left( {x – 7} \right)\\
d){x^3} + 2x – {x^2} – 2\\
= \left( {{x^2} + 2} \right)\left( {x – 1} \right)\\
f){x^2} – 3xy + 2{y^2}\\
= {x^2} – 2xy – xy + 2{y^2}\\
= \left( {x – 2y} \right)\left( {x – y} \right)
\end{array}$