__ What is the length of AB? A. 6 B. 9 C. 3 D. 12

Mathematics

1 answer:

Ira Lisetskai [31]3 years ago

7 0

$\angle A\cong\angle C\ \text{thereofre the triangle ABC is an isosceles triangle}\\\text{Therefore we have the equation:}\\\\4x=2x+6\ \ \ \ \ |subtract\ 2x\ from\ both\ sides\\2x=6\ \ \ \ \ |divide\ both\ sides\ by\ 2\\\boxed{x=3}\\\\AB=4x\to AB=4\cdot3=12\\\\ANSWER:\ D.\ 12$

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Gekata [30.6K]

Answer:

Converting the equation $x^2-20x+13=0$ into completing the square method we get: $\mathbf{(x-10)^2=87}$

Step-by-step explanation:

we are given quadratic equation: $x^2-20x+13=0$

And we need to convert it into completing the square method.

Completing the square method is of form: $a^2-2ab+b^2=(a-b)^2$

Looking at the given equation $x^2-20x+13=0$

We have a = x

then we have middle term 20x that can be written in form of 2ab So, we have a=x and b=? Multiplying 10 with 2 we get 20 so, we can say that b = 20

So, 20x in form of 2ab can be written as: 2(x)(10)

So, we need to add and subtract (10)^2 on both sides

$x^2-20x+13=0\\x^2-2(x)(10)+(10)^2-(10)^2+13=0\\(x^2-2(x)(10)+(10)^2) \:can\: be\: written\: as\: (x-10)^2 \\(x-10)^2-100+13=0\\(x-10)^2-87=0\\(x-10)^2=87$