There are 90 4-digit palindromes
<h3>What are palindromes?</h3>
Palindromes are numbers whose reverse is the same as the original number
<h3>How to determine the count of 4-digit palindromes</h3>
Since the digit is 4, then
- The first digit of the palindrome can be any of 1 to 9 (i.e. 9 digits)
- The second digit can be any of 0 - 9 (i.e. 10 digits)
- The third digit must be the second digit (i.e. 1 digit)
- The last digit must be the first digit (i.e. 1 digit)
So, the total number of digits is:
Evaluate the product
Hence, there are 90 4-digit palindromes.
Read more about numbers at:
brainly.com/question/251701
For # 3 and 5 you need to use the quadratic formula:
<span>(-b +/- srt(b^2 - 4ac))/2a </span>
<span>a, b, and c are representative of this formula: ax^2 +bx + c </span>
<span>1) 2x^2+3x-9=0 </span>
<span>(2x - 3)(x + 3) = 0 </span>
<span>2x - 3 = 0, x + 3 = 0 </span>
<span>+3 +3, -3 -3 </span>
<span>2x = 3, ***x = -3*** </span>
<span>/2 /2 </span>
<span>***x = 3/2*** </span>
<span>2) 5x^2+2x=0 </span>
<span>(x)(5x + 2) = 0 </span>
<span>5x +2 = 0, ***x = 0*** </span>
<span>-2 -2 </span>
<span>5x = -2 </span>
<span>/5 /5 </span>
<span>***x = -2/5*** </span>
<span>4) 4x^2+7x-2=0 </span>
<span>(4x - 1)(x + 2) = 0 </span>
<span>4x - 1 = 0, x + 2 = 0 </span>
<span>+1 +1, -2 -2 </span>
<span>4x = 1, ***x = -2*** </span>
<span>/4 /4 </span>
<span>***x = 1/4***</span>
<span>
Slope = 3
x-intercept = 28/3 = 9.33333<span>
y-intercept = 28/-1 = -28.00000
Hope this helped</span></span>
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