hitunglah nilai dari (√5+√6+√7)(√5+√6-√7)(√5-√6+√7)(-√5+√6+√7) adalah

= (√5²+√30-√35+√30+√6²-√42+√35+√42-√7²)(-√25-√30+√35+√30-√36-√42-√35+√42+√49)
= (5+√60+6+√84-7)(-5-6+7)
= (4+√60+√84)(-4)
= -16-4√60-4√84
= -16-4.2√15-4.2√21
= -16-8√15-8√21