501 Questions To Master GED Test Mathematics_pag199

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501 Questions to Master the GED® Mathematical Reasoning Test
 255. The correct answer is choice c. In order to determine where a 
function hits the x-axis, set y = 0 and solve for x: 
 f(x) = 5x2 – 25
 0 = 5x2 – 25
 Since this quadratic doesn’t have a b term, solve this equation with 
the square root technique. To do this, isolate the b2 and then take 
the square root of both sides:
 0 = 5x2 – 25
 +25 +25
 25__
5 = 5x2___
5
 5 = x2
 Now put the x2 on the left and take the square root of both sides:
 =x 52 = =x 52
 x = =x 52 and x = –=x 52
 So choice c is the correct answer. Choice d mistakenly sets the 
x-intercept equal to y, but y must have a value of 0 at the point 
where the curve hits the x-axis. Choices a and b came about by 
somehow dropping a 5 and taking the square root of 25.
 256. The correct answer is choice c. For each possible value of m, 
there is only one possible value of n.
 Choice a is incorrect. After and including the indicated point, there 
are two possible values of n for each value of m.
 Choice b is incorrect. After the indicated point, there are two 
possible values of n for each value of m.
 Choice d is incorrect. At the indicated point, there are two possible 
values of n for that value of m.
 257. The correct answer is choice a. f(–8) = –2(–8)2 + 1 = –2(64) + 1 = 
–128 + 1 = –127.
 Choice b is incorrect. The exponent on the a indicates a should 
be squared, not multiplied by 2. Further, the result of this will be 
positive instead of negative.
 Choice c is incorrect. The exponent on the a indicates a should be 
squared, not multiplied by 2.
 Choice d is incorrect. The value of (–8)2 is positive, not negative.
501_MathQues_06_161-202.indd 184 7/26/17 4:03 PM