Question

Cho a + b = 5, a.b = 2. Tính A = \(\left(a-b\right)^2\).

Answer 1

\(A=\left(a-b\right)^2=\left(a+b\right)^2-4ab=5^2-4.2=17\)

Answer 2

Answer 3

Lời giải:
$A=(a-b)^2=a^2-2ab+b^2=(a+b)^2-4ab=5^2-4.2=17$

Answer 4

\(\left(a-b\right)^2=\left(a+b\right)^2-4ab=5^2-4\cdot2=25-8=17\)