bantuin yaa hehe

<p>Jawaban yang tepat adalah <strong>C. 400 cm²</strong></p><p>&nbsp;</p><p>Pembahasan :</p><p>p = 50 cm</p><p>l = 40 cm</p><p>L = p x l</p><p>&nbsp; &nbsp; = 50 x 40</p><p>&nbsp; &nbsp; = 2.000 cm²</p><p>Luas karton adalah 2.000 cm²</p><p>&nbsp;</p><p>Luas alas balok yang terbentok adalah 600 cm²&nbsp;</p><p>misalkan sisi persegi = tinggi balok = a</p><p>Luas sisi tegak = Keliling alas x tinggi balok</p><p>2000 - 600 - 4a² = (2((50 - 2a) + (40 - 2a))) x a</p><p>1400 - 4a² = (2(90 - 4a)) x a</p><p>1400 - 4a² = (180 - 8a) x a</p><p>1400 - 4a² = 180a - 8a²</p><p>1400 - 180a - 4a² + 8a² = 0</p><p>4a² - 180a + 1400 = 0</p><p>a² - 45a + 350 = 0 &nbsp; &nbsp; &nbsp; &nbsp;(setelah kedua ruas dibagi dengan 4)</p><p>(a - 10)(a - 35) = 0</p><p>a = 10 cm atau a = 35 cm</p><p>&nbsp;</p><p>a = 35 cm tidak memenuhi syarat karena tidak mungkin panjang sisi perseginya 35 cm. Jadi kita gunakan a = 10 cm</p><p>Luas bagian yang dibuang = 4a²</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; = 4(10²)&nbsp;</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; = 400 cm²</p><p>&nbsp;</p><p>&nbsp;</p>