$\mathrm{ExOO}^{3}$
\[
\left\{\begin{array}{l}
a^{2}-b^{2}=400 \\
a-b=10
\end{array}\right.
\]
(2) Determinier les reels $a$ et $b$ ?
\(\boxed{a = 25, b = 15}\)
Step 1 :Solve the second equation for a: \(a = b + 10\)
Step 2 :Substitute the expression for a into the first equation: \((b + 10)^2 - b^2 = 400\)
Step 3 :Solve the equation for b: \(b = 15\)
Step 4 :Find the value of a: \(a = 15 + 10 = 25\)
Step 5 :\(\boxed{a = 25, b = 15}\)