a. x² + 4x - 21 = 0
a = 1
b = 4
c = -21
x = -b ± √b² - 4ac / 2a
x = -4 ± √4² - 4 (1) (-21) / 2
x = -4 ± √16 - (-84)/2
x = -4 + √16 + 84/2
x = -4 ± √100/2
x = -4 ± 10/2
x1 = -4 + 10/2 = 3
x2 = -4 - 10/2 = -7
b. 2x + 2 + 9x²+ 14 = -22x
9x² + 2x + 14 + 2 + 22x = 0
9x² + 24x + 14 = 0
a = 9
b = 24
c = 16
x = -b ± √b² - 4ac / 2a
x = -24 ± √24² - 4 (9) (14) /2 (9)
x = -24 ± √576 - 576/ 18
x = -24 ± 0/18
x1 = -24 + 0/18 = -4/3
x2 = -24 - 0/18 = -4/3
c. 2x(2x + 1) –10x –16 = 5x²
4x² + 2x - 10x - 16 = 5x²
4x² - 5x² + 2x - 10x - 16 = 0
-x² - 8x - 16 = 0
a = -1
b = -8
c = -16
x = -b ± √b² - 4ac / 2a
x = -(-8) ± √(-8)² - 4 (-1) (-16) / 2(-1)
x = 8 ± √64 - 64/-2
x = 8 ± 0/-2
x1 = 8 + 0/-2 = -4
x2 = 8 - 0/-2 = -4
Espero haberte ayudado. Suerte en los estudios ≧◠◡◠≦.