persegi panjang memiliki panjang (7×-3) dan lebar (×+2) jika keliling nya 78cm tentukan luas!
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K = 2(p + l)
78 = 2(p + l)
39 = 7x - 3 + x + 2
39 = 8x - 1
x = 40/8
x = 5.
p = (7(5) - 3) = 35 - 3 = 32.
l = 5 + 2 = 7.
L = PL = 32 x 7 = 224 cm^2.
Penjelasan dengan langkah-langkah:
Nilai x :
K = 2·(p + l)
78 = 2·(7x - 3 + x + 2)
78 = 2·(8x - 1)
78 = 16x - 2
16x = 78 + 2
16x = 80
x = 5
-----------------------------------
Panjang = 7·5 - 3 = 32 Cm
Lebar = 5 + 2 = 7 Cm
----------------------
Luas :
= p·l
= 32·7
= 224 Cm²