How to solve using quadratic formula: 4x^2+17x-15=0

4x^2 + 17x - 15 = 0
4x^2 + 20x - 3x - 15 = 0
4x(x + 5) - 3(x + 5) = 0
(x + 5)(4x - 3) = 0
x = -5
x = 3/4

Plug in a=4, b=17, c=15 into the quadratic equation.
x= {-b±√(b^2-4ac)}/2a

Have you been taught what the quadratic formula *is*?

If a*x^2 + b*x + c = 0

x = -b +/- sqrt(b^2 - 4*a*c)<>2*a

Over to you and your calculator!

A=4
B=17
C= -15
x= -b plus or minus square root of b^2 - 4(a)(c) all over 2(a)

= ( 4x-3) (x+5)
= 4x^2 + 20x - 3x-15
= 4x^2 + 17x - 15