Exercise 69 Page 175

Area of a triangle is the half of the product of its base and height.

Let's find the area of the triangle above. A=(x+7)(x-2)/2 We know that the area of the triangle is 26 cm^2. By substituting 26 for A in the equation above, we can start to solve the equation for x.

The value of x can be either -11 or 6. Because the measures of the base and height cannot be negative, the value of x must be 6. With this, we can find length of base. Base: x+7 ⇒ 6+7=13 Therefore, the length of the base is 13 cm.