Question

The area of a triangle is 16 square units. The base of the triangle is four more than the height of the triangle. What is the base and height of the triangle?

Answer 1

Answer: "The base of the ∆ is 8 units."

"The height of the ∆ is 4 units."

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Explanation:

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We are asked to find: 1) the base, "b" , and 2) the height, "h", of the ∆ .

Let the height, "h", of the ∆ , equal: "a" units .

We want to find the value for "a" {the height.}.

So; According to the question ,

The base, "b", is 4 units more than: the height, "h", of the ∆ ;

So; the base, "b" = " (a + 4)" units .

If we solve for "a" , the "height",

we can solve for the the base, "b" , which is: "(a + 4)" .

Now; note the formula for the Area, "A", of a triangle:

⇒ Area of ∆ , "A" = ( 1/2 ) × Base × Height ;

that is:

⇒ A = (1/2) × Base × Height .

We are given the Area, "A", of the triangle:

⇒ which is: " 16 unit² " ;

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So; Taking the formula for the Area, "A" , of a triangle:

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⇒ A = (1/2) × Base × Height ;

Let us plug in our given and known/calculated values into the formula:

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⇒ 16 units² = (1/2) × Base × Height ;

⇒ 16 unit² = ( 1/2 ) × ( a + 4 ) × ( a ) unit² ;

So; we multiply both side of the equation by: " 2 " ;

to cancel out the "fraction" on the "right-hand side" of the equation:

as follows:

⇒ 2 × ( 16 unit² ) = 2 × ( 1/2 ) × ( a + 4 ) × ( a ) unit² ;

We see right-hand side that: " 2 * (1/2) = 1 " .

⇒ 32 units² = 1 × (a + 4) × a units² ;

Note: On the right-hand side, we eliminate the " 1 " ;

⇒ since any value(s), multiplied by " 1 " ,

result in those exact same value(s).

⇒ 32 units² = (a + 4) × a units² ;

⇔ (a + 4) × a units² = 32 units² ;

⇔ a (a + 4) units² = 32 units² ;

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To simplify the left-hand side of the equation,

use the distributive property of multiplication;

So we use: a(b + c) = ab + ac ;

⇒ So ; a(a + 4) = a*a + a*4 = a² + 4a.

⇒ We take our equation:

a (a + 4) units² = 32 units² ;

and replace the: " a (a + 4) " ;

with: " (a² + 4a) " ;

to get: " (a² + 4a) = 32 " .

Rewrite as:

" a² + 4a = 32 " ;

Now, subtract " 32 " from BOTH SIDES of the equation:

" a² + 4a − 32 = 32 − 32 " ;

TO GET:

" a² + 4a − 32 = 0 " .

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Now, let's factor the left hand side of the equation; and find the "zeros", or solutions for "a" , when the left-hand side of the equation is equal to "0" ;

⇒ " a² + 4a − 32 ";

To factor:

What factors of "-32" add up to "4" ?

-8 , 4 ? -8 + 4 = ? 4 ? ; -8 + 4 = - 4 ; -4 ≠ 4. So, "no".

8, -4 ? 8 + (- 4) = ? 4 ? ; 8 − 4 = 4 ? Yes!

So, rewrite:

" a² + 4a − 32 = 0 " .

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as: " (a + 8) (a − 4) = 0 " ,

Any value, multiplied by "0" , is equal to "0" .

There are two (2) values being multiplied, that are equal to "0".

So, the equation holds true when:

1) (a + 8) = 0 ; or:

2) (a − 4) = 0 .

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So, 1) when: "a + 8 = 0 ", what does "a" equal?

Add " 8 " to both sides:

⇒ a + 8 − 8 = 0 − 8 ;

to get: "a = - 8 " .

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So, 2) when: "a - 4 = 0 ", what does "a" equal?

Add " 4 " to both sides:

⇒ a - 4 + 4 = 0 + 4 ;

to get: "a = 4 " .

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So, the equation holds true when: "a = 4" or "a = -8" .

Now, we know that "a" refers to the height. The "height" cannot be a "negative" number ⇒ So we use " a = 4 " . The height is: " 4 units."

The base is "4 units more than the height" ; so the base is:

⇒ { "4 units" + "4 units" = " 8 units " .}.

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" The base of the ∆ is 8 units. "

" The height of the ∆ is 4 units. "

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