Answer: 10 inches.
Explanation:
We have to solve a system of equations.
The formula to calculate a triangle area is A = (b.h)/2
where b is the base and h is the height. This will be our first equation.
Since the height is 4 inches greater than the base, the second equation will be: h = b+4
We replace h and the value of the area (70 square inches) in the first equation, and we solve it by using the cuadratic equation formula:
70 = (b . (b+4)) / 2
70 . 2 = b² + 4b
140 = b² +4b
0 = b² + 4b - 140
The roots of this polynomial are -14 and 10. Since a distance can't be negative, the length of the base is 10 inches.