2a + 2b = The perimeter. You know one side (5cm) and the total perimeter (30cm)So your equation should be 2(5) + 2(b) = 30. From here you simply solve for "b" 2(b) = 30 -10 2(b) = 20 b = 20/2 b is equal to 10cm.
X^2 + 2x - 3 = (x-1)(x+3)
B Because you can just ask Siri if you want to