A rectangle has length (x + 5)cm and width (x –2)cm. Its area is 60 cm^2. What is x?
A rectangle has length (x + 5)cm and width (x –2)cm. Its area is 60 cm^2. What is x?
Length times Width equals Area. So, (x + 5)(x – 2) = 60
Multiply it out and subtract 60 from both sides x2 + 3x – 10 – 60 = 0
x2 + 3x – 70 = 0
Factor it (x + 10)(x – 7) = 0
x = –10 and x = 7
You can't have a negative side so discard that one which leaves x = 7
.
