SAT Math XVIII

Algebra Level 1

Let f ( x ) = x 2 − 5 f(x)=x^2-5 . If f ( 6 ) − f ( 4 ) = f ( y ) f(6)-f(4)=f(y) , what is ∣ y ∣ \left| y\right| ?


The answer is 5.

John M. by John M. , 24, USA

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2 solutions

Syed Hamza Khalid
Aug 21, 2018

The answer is in the picture. That's what I did

3 Helpful 0 Interesting 3 Brilliant 0 Confused

P u t x = 6 a n d x = 4 i n f ( x ) = x 2 − 5 : 36 − 5 − 16 + 4 = f ( y ) 20 = y 2 − 5 25 = y 2 y = ± 5 ∣ y ∣ = 5 Put\quad x=6\quad and\quad x=4\quad in\quad f(x)={ x }^{ 2 }-5:\\ 36-5-16+4\quad =\quad f(y)\\ 20\quad =\quad { y }^{ 2 }-5\\ 25\quad =\quad { y }^{ 2 }\\ y\quad =\quad \pm 5\\ \left| y \right| \quad =\quad 5

Cheers!!!:):)

3 Helpful 0 Interesting 0 Brilliant 1 Confused

Why did you write the answer in the question ?

Soumo Mukherjee - 6 years, 7 months ago

I did it the same way

Abdur Rehman Zahid - 6 years, 7 months ago

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