Toán Lớp 8: Bài 1
a) (5x + 1)^2 – (5x + 3 ) (5x – 3)
b) (x + 3 )^2 + (x – 2 )(x + 2) – 2 (x – 1 )^2
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Toán Lớp 8: Bài 1
a) (5x + 1)^2 – (5x + 3 ) (5x – 3)
b) (x + 3 )^2 + (x – 2 )(x + 2) – 2 (x – 1 )^2
Làm giúp mik nhé
Comments ( 1 )
a){\left( {5x + 1} \right)^2} – \left( {5x + 3} \right)\left( {5x – 3} \right)\\
= 25{x^2} + 10x + 1 – \left( {25{x^2} – 9} \right)\\
= 25{x^2} + 10x + 1 – 25{x^2} + 9\\
= 10x + 10\\
b){\left( {x + 3} \right)^2} + \left( {x – 2} \right)\left( {x + 2} \right) – 2{\left( {x – 1} \right)^2}\\
= {x^2} + 6x + 9 + {x^2} – 4 – 2\left( {{x^2} – 2x + 1} \right)\\
= 2{x^2} + 6x + 5 – 2{x^2} + 4x – 2\\
= 10x + 3
\end{array}$