Question

Scoateți termenii de sub radical apoi calculatii :
$a) - 3 \sqrt{20} + \sqrt{80} - \sqrt{405}$
$b) \sqrt{32} - \sqrt{8} + \sqrt{98} - 5 \sqrt{18}$
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Answer 1

Răspuns

a) - 11√5

b) - 6√2

Rezolvare

a) √20 = √4*5 = 2√5

√80 = √16*5 = 4√5

√405 = √81*5 = 9√5

- 3√20 + √80- √405 =

= - 3*2√5 + 4√5 - 9√5

= - 6√5 + 4√5 - 9√5

= - 11√5

b) √32 = √16*2 = 4√2

√8 = √4*2 = 2√2

√98 = √49*2 = 7√2

√18 = √9*2 = 3√2

√32 - √8 + √98 - 5√18 =

=4√2 - 2√2 + 7√2 - 5*3√2

=4√2 - 2√2 + 7√2 - 15√2

= - 6√2