1d
3b
4b
5a
7a
8b
9d
10c

b

đặt biểu thức trên là A ta có
A=√4−√7+√4+√7
\(A^2=\left(\sqrt{4-\sqrt{7}}+\sqrt{4+\sqrt{7}}\right)^2\)
\(A^2=4-\sqrt{7}+2.\sqrt{\left(4-\sqrt{7}\right)\left(4+\sqrt{7}\right)}+4+\sqrt{7}\)
\(A^2=8+2.\sqrt{16-7}\)
A²=8+2.3
A²=14
A=\(\sqrt{14}\)

1c
2b
3c
4b
5b

2m² 30dm²=23 000cm²
4m² 8cm²=40 008 cm²
7 075cm²=70 dm² 75cm²
504cm²=5dm² 4cm²

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\(A=x^2-4x+1\)
\(A=x^2-4x+4-3\)
\(A=\left(x-2\right)^2-3\)
Min A = -3
Min A xảy ra khi (x-2)²=0
                           x-2=0
                           x=2
 

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6.10²¹
5.10¹⁵