Ta có : \(4a^2-\left(a+b\right)\)
= \(\left(2a\right)^2-\sqrt{\left(a+b\right)}^2\)
= \(\left(2a-\left(a+b\right)\right)\left(2a+\left(a+b\right)\right)\)
= \(\left(2a-a-b\right)\left(2a+a+b\right)\)
= \(\left(a-b\right)\left(3a+b\right)\)
Ta có : \(4a^2-\left(a+b\right)\)
= \(\left(2a\right)^2-\left(\sqrt{\left(a+b\right)}^2\right)\)
= \(\left(2a-\sqrt{a+b}\right)\left(2a+\sqrt{a+b}\right)\)