Câu 1: Toán đa thức, phân thức
a/ ( 5x + 3 )( 2 – x )
b/ ( x – 1 ) ^2 + 4x ^2 – 5x
c/ ( x – 3 )( x + 3 )
d/ ( x + 3)(x – 3 ) – x ^2
e/ ( x – 2 )( x + 5 ) + x ( 2 – x )
f/ ( x – 3 ) ^2 + x ( 6 – x )
Câu 1: Toán đa thức, phân thức
a/ ( 5x + 3 )( 2 – x )
b/ ( x – 1 ) ^2 + 4x ^2 – 5x
c/ ( x – 3 )( x + 3 )
d/ ( x + 3)(x – 3 ) – x ^2
e/ ( x – 2 )( x + 5 ) + x ( 2 – x )
f/ ( x – 3 ) ^2 + x ( 6 – x )
Đáp án:
$\begin{array}{l}
a)\left( {5x + 3} \right)\left( {2 – x} \right)\\
= 10x – 5{x^2} + 6 – 3x\\
= – 5{x^2} + 7x + 6\\
b){\left( {x – 1} \right)^2} + 4{x^2} – 5x\\
= {x^2} – 2x + 1 + 4{x^2} – 5x\\
= 5{x^2} – 7x + 1\\
c)\left( {x – 3} \right)\left( {x + 3} \right)\\
= {x^2} – 9\\
d)\left( {x + 3} \right)\left( {x – 3} \right) – {x^2}\\
= {x^2} – 9 – {x^2}\\
= – 9\\
e)\left( {x – 2} \right)\left( {x + 5} \right) + x\left( {2 – x} \right)\\
= \left( {x – 2} \right)\left( {x + 5} \right) – x\left( {x – 2} \right)\\
= \left( {x – 2} \right)\left( {x + 5 – x} \right)\\
= \left( {x – 2} \right).5\\
= 5x – 10\\
f){\left( {x – 3} \right)^2} + x\left( {6 – x} \right)\\
= {x^2} – 6x + 9 + 6x – {x^2}\\
= 9
\end{array}$
a) (5x + 3) (2 – x)
= 10x – 5x² + 6 – 3x
= 7x – 5x² + 6
b) (x – 1)² + 4x² – 5x
= x² – 2x + 2 + 4x² – 5x
= 5x² – 7x + 2
c) (x – 3) (x + 3)
= x² – 9
d) (x + 3) (x – 3) – x²
= x² – 9 – x²
= -9
e) (x – 2) (x + 5) + x (2 – x)
= x² + 5x – 2x – 10 + 2x – x²
= 5x – 10
= 5 (x – 2)
f) (x – 3)² + x (6 – x)
= x² – 6x + 9 + 6x – x²
= 9
NHỚ VOTE CHO MÌNH 5 SAO NHA!