Toán Lớp 8: giúp mik vs ạ vote cho hay nhất nha
phân tích thành nhân tử
x ³-3a+3b-b ³
x ²-y ²+12y-36
x ²-2020x-2021
4x ²-25+(2x+7)(5-2x)
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Toán Lớp 8: giúp mik vs ạ vote cho hay nhất nha
phân tích thành nhân tử
x ³-3a+3b-b ³
x ²-y ²+12y-36
x ²-2020x-2021
4x ²-25+(2x+7)(5-2x)
Comments ( 1 )
a){a^3} – 3a + 3b – {b^3}\\
= \left( {{a^3} – {b^3}} \right) – \left( {3a – 3b} \right)\\
= \left( {a – b} \right)\left( {{a^2} + ab + {b^2}} \right) – 3\left( {a – b} \right)\\
= \left( {a – b} \right)\left( {{a^2} + ab + {b^2} – 3} \right)\\
b){x^2} – {y^2} + 12y – 36\\
= {x^2} – \left( {{y^2} – 12y + 36} \right)\\
= {x^2} – {\left( {y – 6} \right)^2}\\
= \left( {x – y + 6} \right)\left( {x + y – 6} \right)\\
c){x^2} – 2020x – 2021\\
= {x^2} – 2021x + x – 2021\\
= \left( {x – 2021} \right)\left( {x + 1} \right)\\
d)4{x^2} – 25 + \left( {2x + 7} \right)\left( {5 – 2x} \right)\\
= \left( {2x – 5} \right)\left( {2x + 5} \right) – \left( {2x – 5} \right)\left( {2x + 7} \right)\\
= \left( {2x – 5} \right)\left( {2x + 5 – 2x – 7} \right)\\
= \left( {2x – 5} \right).\left( { – 2} \right)\\
= 2\left( {5 – 2x} \right)
\end{array}$