Question

Please please please can anyone solve this equation:
$15d ^{2} - 36d - 144 = 0$


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Answer 1

Answer:

$d = \frac{6}{5}+ \frac{2\sqrt{69} }{5}$   ,  $\frac{6}{5}- \frac{2\sqrt{69} }{5}$

Step-by-step explanation:

15d^2 - 36d - 144 = 0

Divide both side by 15

(15/15)d^2 - (36/15)d - (144/15) = 0/15

d^2 - 12/5(d) - (48/5) = 0

Add (48/5) to both side

d^2- (12/5)d = 48/5

Now we will complete the square

((12/5)/2)^2 = 36/25

We will add 36/25 to both sides

d^2- (12/5)d+36/25 = 48/5 + 36/25

d^2- (12/5)d+36/25 = 276/25

(d-6/5)^2 = 276/25

solve for d

$d = \frac{6}{5}+ \frac{2\sqrt{69} }{5}$   or $\frac{6}{5}- \frac{2\sqrt{69} }{5}$