please jawab pake cara yaa No1. 7+3x=14-2x. No2. 2a(a+5)-2(a+4)=0. No 3. 5(7x-3)-3(7x-3)=x+7. No 4. diberikan sebuah segitiga ABC dgn panjang sisi AB=(x+3)cm,

Mapel : Matematika
Kelas : VII SMP
Bab : Aljabar

Pembahasan :
1.

7 + 3x = 14 - 2x
3x + 2x = 14 - 7
5x = 7
x = 7/5

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2.

2a(a + 5) - 2(a + 4) = 0
2a² + 10a - 2a - 8 = 0
2a² + 8a - 8 = 0
a² + 4a - 4 = 0

Rumus ABC
a = -2 + 2√2
a = -2 - 2√2

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3.

5(7x - 3) - 3(7x - 3) = x + 7
35x - 15 - 21x + 9 = x +7
14x - 6 = x + 7
13x = 13
x = 1

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4.

Keliling = 30,5
AB + BC + AC = 30,5
(x + 3) + (2x - 1) + (3x - 1) = 30,5
6x + 1 = 30,5
6x = 29,5
x = 4,9..
x = 5

AB = x + 3 = 8 cm
BC = 2x - 1 = 2(5) - 1 = 9 cm
AC = 3x - 1 = 3(5) - 1 = 14 cm