\(A\left(x\right)=2x^2+2x+3\)
3) \(A\left(x\right)=3\)
khi đó: \(2x^2+2x+3=3\)
<=> \(x^2+x=0\)
<=> \(x\left(x+1\right)=0\)
<=> \(x=0\)
hoặc \(x=-1\)
A(x) = 3x2 + x3 + 5x4 - x2 - x3 - 5x4 + 2x + 3
= 2x2 + 2x + 3
A(x) + B(x) = 2x - 7
<=> ( 2x2 + 2x + 3 ) + B(x) = 2x - 7
B(x) = 2x - 7 - ( 2x2 + 2x + 3 )
= 2x - 7 - 2x2 - 2x - 3
= -2x2 - 10
A(x) = 3 <=> 2x2 + 2x + 3 = 3
<=> x( 2x + 2 ) = 0
<=> x = 0 hoặc 2x + 2 = 0
<=> x = 0 hoặc x = -1
3, A(x) = 2x2 + 2x +3
Ta có : A(x) = 3
\(\Leftrightarrow\)2x2 + 2x + 3 = 3
\(\Leftrightarrow\)2x2 +2x = 0
\(\Leftrightarrow\)2x ( x + 1 ) = 0
\(\Leftrightarrow\)2x = 0 hoặc x + 1 = 0
\(\Leftrightarrow\)x = 0 hoặc x = -1
Vậy x = 0 hoặc -1 khi A(x) = 3