The base of a triangle is four less than three times the height. The area of the triangle is 38 square centimeters. A=(b×h)/2

(3 points)

1 answer

To solve for the base and height of the triangle, we can use the formula for the area of a triangle:

\[ A = \frac{b \times h}{2} \]

Given:

  • The area \( A = 38 \) square centimeters.
  • The base \( b \) is four less than three times the height \( h \).

We can express the base \( b \) in terms of the height \( h \):

\[ b = 3h - 4 \]

Now we can substitute this expression for \( b \) into the area formula:

\[ 38 = \frac{(3h - 4) \times h}{2} \]

Next, we'll multiply both sides by 2 to eliminate the fraction:

\[ 76 = (3h - 4) \times h \]

Expanding the right side:

\[ 76 = 3h^2 - 4h \]

Now, rearranging the equation to set it to zero:

\[ 3h^2 - 4h - 76 = 0 \]

Next, we will use the quadratic formula to solve for \( h \). The quadratic formula is:

\[ h = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \]

Here, \( a = 3 \), \( b = -4 \), and \( c = -76 \). Plugging in these values:

\[ h = \frac{-(-4) \pm \sqrt{(-4)^2 - 4 \cdot 3 \cdot (-76)}}{2 \cdot 3} \] \[ h = \frac{4 \pm \sqrt{16 + 912}}{6} \] \[ h = \frac{4 \pm \sqrt{928}}{6} \] \[ h = \frac{4 \pm 4\sqrt{58}}{6} \] \[ h = \frac{2 \pm 2\sqrt{58}}{3} \]

Calculating the positive value since height cannot be negative:

\[ h = \frac{2 + 2\sqrt{58}}{3} \]

Now, we can calculate \( b \) using \( b = 3h - 4 \):

\[ b = 3\left(\frac{2 + 2\sqrt{58}}{3}\right) - 4 \] \[ b = (2 + 2\sqrt{58}) - 4 \] \[ b = 2\sqrt{58} - 2 \]

Thus, the height \( h = \frac{2 + 2\sqrt{58}}{3} \) and the base \( b = 2\sqrt{58} - 2 \).

To approximate the numerical values:

\[ \sqrt{58} \approx 7.616 \] Thus:

\[ h \approx \frac{2 + 15.232}{3} \approx \frac{17.232}{3} \approx 5.744 \text{ cm} \] \[ b \approx 2(7.616) - 2 \approx 15.232 - 2 \approx 13.232 \text{ cm} \]

Finally, the height and base of the triangle are approximately:

\[ h \approx 5.74 \text{ cm}, \quad b \approx 13.23 \text{ cm} \]