Question

cac cau oi giup to

Answer 1

Tìm GTNN:
a. M = x² - 8x + 5
M = ( x^2 - 2.x.4 + 16 ) - 11
M = ( x- 4 )^2 -11
Vì ( x- 4 )^2 > hoặc = 0 vs mọi x
=> ( x-4)^2 -11 > hoặc = -11 vs mọi x
=> M > hoặc = -11 vs mọi x
Vậy min M = -11 <=> ( x- 4 )^2 = 0
<=> x = 4

Answer 2

a, A = x² - 6x + 10
A=( x^2 - 2.x.3+9 ) +1
A = ( x- 3 )² +1
Thay x= 103
A = ( 103 - 3 )² +1
= 100^2 + 1 = 10000+ 1 = 10001
b, B = x² -10x + 25
B = x^2 - 2.x.5 + 52
B = ( x- 5 )²
Thay x = 25
B = ( 25 - 5 )²
B = 20^2 = 400